You should usually have to raze a fortress to the ground, rather than capture it. While that may not be historically accurate, it makes sense given the style of RTS, rather than something like Total War.

If I recall correctly, Roman Army Camp used to be able to hold 40 soldiers. Granted, when the collision issue (or just the formations exploit) is fixed, a full Fortress will be almost impossible to capture at full health, which might be a good thing lol. 

From this initial post you made, it doesn’t come across as an additional idea but rather as a solution to the problem of buildings being too easy to capture. That is: instead of increasing capture resistance, allowing more units to garrison inside. That’s why I responded the way I did.   What I mean is that, from a gameplay perspective, it seems much more interesting to improve the capture points of buildings and be able to keep more units outside, actively engaged in combat. If you garrison 40 or 50 units out of an army of 150, the enemy will most likely be able to wipe out the remaining forces due to overwhelming numerical superiority. I’m not opposed to increasing the garrison capacity of forts/CCs or other important buildings per se. But when it’s proposed as a solution to the issue of rapid capture, I think it’s better to directly strengthen capture resistance instead. As for the historical aspects, I understand them, but this is a game and, as such, it relies on certain abstractions.

Calling the fortress just a single building overlooks how central it can become in many matches. There are moments when players feel like they’ve lost the match the instant they lose it. Historically too, it is far from a simple building. It is a defensive structure placed in strategic locations, capable of shaping and altering the course of events. Whether I choose to implement it or not is another matter but it would make perfect sense for such a defensive complex to be able to hold 40 or 50 units especially in a game where the single building Wonder can already accommodate up to 50.  Here is The German Wonder, which is just a ruined Roman camp, can still garrison 50 units, roughly 33% of a 150 soldiers.    P.S. I’m not against the idea of increasing capture resistance.

This is what we are talking about with formation exploit: formation capture exploit.mp4 And this: formation gathering exploit.mp4   The problem with this approach is that, if you need to garrison, say, around 40 units to prevent your building from being captured, out of an average of 150 soldier units you might have in a 200 pop game, you end up dedicating 26% of your units just to guarding a single building. It makes more sense to increase capture resistance.