Oh, you even wrote yourself a roadmap for chars. Well dude, you're cool :-)
Well, let's see what comes of this. In theory, it should turn out okay.

Спойлеры - вещь хорошая: всегда знаешь, что будет.

Then you're doing everything right.

Regarding the advantages of 2D - yes, here you are limited only by your imagination and endurance, 3D requires more time and tends to become an avalanche-like complication when trying to make something more than just a human or a… tank. In 3D you can do, for example, girls, and even then not all of them, but only those whom you focus on often, and leave everything else to 2D, well, you’ll understand this better than me ;-)

Звук соударения световых мечей через 3… 2…

I offer you this option: make the main characters in 3D, and continue to draw any extras by hand if it doesn’t bother you. You really have a lot of characters, but you can always distinguish the main ones and the secondary ones. Otherwise, you'll get tired of converting everyone to 3D alone.
In general, you also can try to make some extra backgrounds using a neuron: Bing generates them quite well, for example.

And make a backup of the base to an external drive, in case of unforeseen situations. You have fucking awesome models, so wouldn’t want to lose them.

Рестлинг пейсюнами! Оу май!

Think, you can try to combine 3D and 2D chars. At least for the sake of experiment ;-)

Кстати, вампирша получилась очень приятная, с приятной цветовой гаммой.
И вообще, мне нравятся отрёхмеренные персонажи, они у Локомотива получились прикольные.

Они обе на стол забрались.

Не должна, она со стола падает.