"Castle" upgrades

[Axalon]

Am I right in thinking that the advantage in constructing the in-between levels (e.g. ballista towers, catapult towers) is that a castle will automatically downgrade one "level" if taken by storm, so it's a way to prevent losing your whole upgrade?

And...

It's been very long since I last played M:TW, but I think that was the case. It's a dubious benefit, however, since you will have lost the castle to the enemy anyway. And because the basic structure isn't downgraded, you will have to spend longer besieging it (or storm it while it contains a greater garrison) to retake it.

Nah, it is da other way around... A Castle takes damage/downgrades if one takes it by siege, and no damage if it is taken by storm. I have many times stormed castles because I did not want them to downgrade. So, the whole point of upgrading castles between each major stage (Keep --- Castle etc.) is nominal - it does get slightly tougher to storm by each upgrade (and to siege too?). All max garrison levels are standardized with the big 4-5 stages so there is no change/gain to be had there (in raw MTW anyways).

One can do little about all this in terms of modding. I certainly tried, but with
only a few parameters to work with, one can only take these things so far.

- A