The difference between business-as-usual ("BAU") work and a change initiative can be nicely described with a story.
Say, you have an old-style 19th century army, and you want to move part of it, say, a battalion, through to the other side of the country. I am picking the 19th century, as army leadership tactics have changed quite drastically in the last few decades. But this is a traditional army.
There will be challenges – you need to find the best roads for your army, you need to find shelter on the way, and you need to find people who will sell you the supplies you need. Since you are not the first one who leads an army through that particular country, there will be procedures that will tell you what you have to do initially, and there will be backup procedures that will tell you what you will do when things go wrong, who to escalate it to, who the backup supplier is, etc. At some point in history, any of these things were new challenges for someone, but the problems around them have long been solved.
So, if your army were to come to, say, a big river, then the procedure may tell you that you do NOT try to swim across with your battalion, and you do NOT try to build your own bridge, but instead, you will send a scout to either side to find the nearest bridge that is safe, and then you will lead your army over that nearest bridge and move on. That makes sense, because most of your people cannot swim, and if you were foolhardy enough to try make them swim across the river or build your own bridge, you may kill half your people in the process – that does not make sense just to save half a day or so, if you are in no great hurry, because nobody cares if the war starts half a day later.
This is BAU work.
Now consider that you are still leading that same army through a country, but it is a foreign country that has not been mapped out yet. Then suddenly you find yourself and your army blocked by a mass of water again. So, you send out your scouts left and right, but when they come back, they do not report that they found any bridges, but instead, that all the bridges have been blown up, there were two rivers on either side of your army, and they are now converging in front of you – and an enemy army outnumbering you 10 to 1 is half a day behind you.
This is an urgent change project. Not all change projects are like that, but we have worked on change projects that would fit that description - not that we would want to compare a regulator to an enemy's army, but the pressure on an organisation can be similar in terms of time and consequences - you get the picture.
So what now? Your normal strategy has not worked, your backup plan does not work either, and the enemy is about to wipe you out. Do you just tell your people to swim through a river or build a bridge? You know these are people who cannot swim and have never built a bridge before in their lives? No, that would be foolish.
That’s where the change manager and the SMEs come in. The change manager is they guy who has dealt with unusual situations before, who has seen several variations of what you need to build previously, who has some special skills, who is creative enough to find a vision, and who has the stubbornness to see it through no matter what, while the SMEs provide the technical expertise others do not really need in BAU work, because in BAU work, the setup was long done.
So, your change manager then comes in and sees that large tree on the other side. He takes a rope, makes a loop, shoots the loop over a branch of the tree, pulls the rope tight and then takes a second rope, walks over the tight rope in order to fasten the second rope on the other side as well. When he is almost over, the rope on the other side comes loose, and he almost crashes down into the ravine, but he manages to get a hold of a branch in the rock 20 feet down, and climbs up the sheer cliff face - in one of his previous jobs he had to learn free-climbing, which comes in useful now. The SMEs then go ahead and build the rest of the makeshift bridge. Two SMEs fall into the water, but as it happens, they learned in a previous job how to dive into water from a great hight, and they are excellent swimmers. So they swim ashore, walk back, and climb up the cliff again. They don not go to the approved suppliers for the wood they need, because there are no approved suppliers with the enemy army behind, but they do not have to – in BAU there are approved suppliers so that your junior guys do not have to figure out themselves if the material is good enough to do the job. Here, the SMEs are senior – they are experts in their field, so they can tell which materials will do the job, maybe even better than the standard, and they know what the impact is of what they are doing and how they need to compensate if they do not find exactly what they are looking for.
All the while, your BAU staff is entertained, eating popcorn while watching the show. Some BAU staff is chipping in, as they have some special skills as well and wanted to do this forever themselves, some are keen to chip in but not quite there yet in terms of skill, but they give great suggestions, others stay way in the back and swear to never go near that bridge until it is safe and they have seen half the army walk over it. Those are the ones who say "It'll never work".
Again, would you want to use your regular BAU staff to do build the bridge? Unless they have some skills you never knew about, probably not. Some of them would end up falling down and drowning in the river, and they may not have the expertise to build a bridge that is sturdy enough to hold an army even just once.
Is change staff therefore better than BAU staff, should you only hire change people from now on? Not at all. Change people are good at what they do, and they tend to have a variety of skills, and a breadth of knowledge from having worked on different projects, but they also don't do well in a BAU environment and quickly get bored - then they start to improvise, if you like it or not. Your BAU staff is likely better at their regular job than the change manager or SME would ever be, but they are usually loyal to the organisation, which means they have not seen as many similar solutions as change people have on different projects and are likely not as good at improvising – because they are not supposed to do that in BAU work, so they do not have the practice. BAU staff enjoy procedures and consistency, and can more or less automate your business in terms of procedures, to make it safe for junior staff and newcomers. This is what your business will need after the change.
So you've got a makeshift bridge now. When the enemy army comes, you send your army over that bridge – if your change manager and the SMEs were good, the bridge holds, you can defend it from the other side and wait until your reinforcements come and take care of the enemy, or the enemy simply goes away because they are happy that you are now on the other side of the river.
THEN have your BAU guys built it out into a proper bridge with all the right materials and safety measures that you would expect in BAU work, so that the rest of the army, i.e. the other battalions, can follow safely, and the bridge can in future be used by civilians as well. The change manager and the SMEs will have left instructions of what is vital to be observed, but it will likely only be the must-haves and the really nice to haves. Your BAU staff can then add all those pieces that are unique to your culture and that add additional convenience.
Therefore, both change and BAU staff/contractors and/or consultants are needed, and both have their place. Ideally, they listen to each other and compliment each other.