So, I HAVE read all the rules now.
Indeed, the problem is really Destroyer weapons, nothing else.
The "optional" building rules in stronghold, I really don't understand why they're the optional bit, they're really what the fortification rules should have been from the beginning. This is a big case where it should have been a FAQ, but GW thinks they get to charge you money for it. (hint, I didn't pay money for it, and I don't feel even a little guilty) I'm not sure I understand why all buildings should essentially come with assault ramps for free, now, but I also don't really have a problem with it.
All the new buildings and add-ons seem fine, too. (except the D weapons) The whole complexes...things that let you take 3 bastions, multiple aegis lines and guns, those seem a little silly. I don't mind those from a balance perspective, more just that it'd feel like I'm playing with my castle greyskull action set (tm).
I also have no problem with superheavies (though I think they are, almost without exception, kind of silly), just the D weapons.
In the end, I think we definitely should use the new building rules, and I'm fine with using the all the rest of it, as long as we convert D weapons to Str 10 AP1. I would also ban all the mega-blast type stuff, limit everything to large blast or smaller. (frisbee size damage templates are dumb)
I think it's fine to have more Str 10 in the game. There's a lot of Space marines on bikes, Iridium commanders, demon princes, et all, taht need to fear for their lives a bit more.