It would really be nice to resurrect this thread. The important part is having a dedicated moderator (who until now has been the ever-diligent Meneth), though. It's nearly useless without such a dedicated moderator to constantly keep the OP list concise, categorized, prioritized, and screened for, frankly, irrelevancy or redundancy.
People should be able to add requests as they like to the thread but be expected to be asked to drill-down specifics and for an actual use case before their item is added to the OP. That way, devs can read the updated OP (only) now and then and see in very precise terms modding suggestions that they'd probably not even thought to include and that are self-evidently valuable from their concise description alone. The moderator should probably also be a pretty good modder so that he/she can quickly spot what can already be done.
Meneth was pretty good at that. The current OP list needs to be re-evaluated, unfortunately, as a lot has been implemented since many items' addition. His energy seems directed elsewhere lately, though I'm just happy to have him back at CKII modding recently with his upcoming re-worked faction system for PB.
I fit all those requirements to moderate this list. I'd consider taking it over and maintaining it if he would prefer to hand it off, although I am somewhat recalcitrant to offer since:
a) it's his thread, and I'm not sure he has any intention to actually retire it.
b) I'm not so convinced that 'improvements to modding' are near the top of the current CK2 dev team's priority list anymore and would love some reaffirmation from their current dev team-- as the relatively mod-basic EU4 is, in some areas, making strides past the otherwise superior CK2 modding support in its upcoming patch 1.4 with full variable support (yay!), all sorts of other fulfilled modder requests, and devs that are actively talking to modders on the EU4 modding forums (thanks, Captain Gars) for input on how they can help make the game more extensible. Mind you, patch 2.0 addressed a lot of advanced stuff, but it didn't really grant much new power to modding, considering the span since 1.10.
c) it's a lot of work to actively maintain this list to the level of standards required to be useful to devs and therefore have any impact, and due to (b), are devs even going to pay attention to that work at this point? I'm just not sure.