Hi, I wanna join! Can I?
Adding new paths to dom3 and making them moddable is less likely than us making a dom4.
Programming-wise it would be a hassle. A bigger hassle than making new code. Thus dom4 is more likely. Many examples on unforeseen problems has already been posted, including UI stuff, AI stuff and gem management: how much more gem production must rise to compensate for sites being less easy to find, and how many traits a given site must accomodate etc.
Endo's suggestion on themes is way easier. Some of the theme structure is still in the code in the form of nation's dom-effects and it is partially moddable.
Adding nation based blesses is also easier by far. It just needs an entirely new modding capability and bless structure. Probably a lot more demanding than site modding.
Thematically I'm inclined to think that the need is slim. I have at times thought that the current paths could have been better chosen. You can make new magic traditions under the current system just by adding a description and possibly a nation restriction. If you want a tantric tradition you can add a couple of tantric spells to the Bandar Log, describe the practices and how this is a sister path of the astral magic.
Sex magic might be conceived as a technique deriving it's powers from necrophilia (death), wild magic (nature), carnal energies (blood with or without sacrifices) or something else. It's all in the descriptions.
At times I have thought about just having three paths. Ctonic, oceanic and olympic (or whatever you want to call them). Most phenomenon and gods fall under these three spheres. Then you could give each nation a set of unique spells associated with the three godly spheres of influence, instead of the current plethora of spells.
This would of course mean less diversity for each nation and possibly more thematic congruence. It would make my game more coherent, but would probably lessen the strategic options of the game.
Adding new paths on the other hand would not be that meaningful unless the current paths were differentiated and new effects and options were added. Death magic could be remade into reanimation, necromancy (divination and ghost summonings), darkness (including HB's shadow stuff) and unlife (drain life, cloud of death, disintegrate), but that is to some extent covered by the schools of magic. Paths overlap a bit atm, but if there was multiple new paths the overlap would have to be lesser and current paths would need to be conformed I think.
Hmm, not sure if I said what I intended, but never mind. I said something