I have three broad categories of requests, and then a thought about base PvP:
My first request feels to me like low-hanging fruit, like it ought to be easy. Go through the list of items that can be used as interact-able objectives in AE missions, all the boxes and safes and stuff. Make a list of the ones that don't have matching base items, and import them. It feels like this ought to be pretty easy because by definition they all have separate geometry files, right?
My second request is one I make every time, but especially after the last round of improvements to Winter Forest: we need more seasonal holiday decor! Halloween is sort of covered, with multiple jack-o-lantern models, plenty of existing spooky trees, all the creepy decor pieces from the Talons of Vengeance sets. But every year it astonishes me that we don't have a single Christmas tree, a single wreath, a single strand of holiday lights -- the only winter holiday decor we have in the game is a couple of menorah models. There are multiple 3D models in the game for wrapped Christmas presents (from the open zone event), how hard would it be to import those as base decor? And oh, how much I wish, every year, that we could place ice-skating patches in our bases. There's a Valentine's Day event, but no Valentine's Day decor, either.
My third request is that I'd like a whole re-think of all of the non-interact-able NPCs and their placement. Right now, each NPC in the base editor has one idle animation. You get a couple of NPCs holding torches, and only those NPCs can hold torches, and that's all those NPCs can do, and so on. What I'd like is to be able to place any combat or hostage NPC that can be used in AE (except for custom characters, for obvious reasons) and then, in the Object Info panel when that NPC is selected, have a pull-down menu of every possible stance or idle animation.
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As for base PvP, it's worth talking about why it never worked before we put any development resources into it. For one thing, CoH is a hard game to design PvP for -- you have the unhelpful combination of 80 MPH travel powers and long-activation combat powers that root the attacker. But base PvP was also super-punishing for anybody with pet or pseudo-pet powers, because bases don't get a map optimization pass like mission maps and city maps do, so there are no pre-calculated NPC paths for them to follow. For another, they create an inherent scheduling crisis: if both the attackers and the defenders don't show up at the same time, and in roughly equal forces, it's no fun for either or both side. I don't see any way to fix any of those problems.
I can only really think of one PvP add-on to bases that wouldn't create some intractable headache. You could, in theory, add another room type to the Add Room tab for PvP rooms of various sizes that would use, say, Warburg combat rules, where you can attack anybody who isn't on your team. But because the NPC pathing issues are never going to go away, you'd have to make it impossible to place objects in those rooms, they'd have to be just empty boxes -- skinnable with the usual textures, but empty. Otherwise, the engine just doesn't support it well enough.