Kimera allows simple edits, but if you trully want to work on models, treat it like a program you'll use to test and correct allignment of your model, not make it there.
A few steps for "true" changing models.
- Firstly start from getting original battle models from your game, by unpacking battle.lgp using unlgp or even lgptools.
- Find info here in the forum which files are what as that'll be your most usefull knowledge for any kind of modding.
- Get a 3D modelling program 3Ds max 7+(7+ means "at least v7") or Blender. Blender is free and it's much easier to model with, but converting your model back to the game will take more time.
- Get "biturn" and convert models you want to change to ASE(if you're using 3ds max) or OBJ(in case of Blender).
- Now fun part - import those to your 3d modelling program and you can do whatever you want. Make note that it doesn't really matter if you just correct those parts you import or do full character model anew, in the end you'll need to cut it on about same parts you want to change and to simplify later work you need to allign those new parts in same positions as those you got from game.
- Export each part of your new model as 3DS(if using 3dsmax) or as obj(in case of blender), make note you'll need to use biturn to convert that obj to 3ds here couse blender doesn't really export to 3ds everything you wish it would, and you need 3ds model for next step.
- Open each part, one by one in a program you can also get here called - PCcreator, correcting UVmap, adding texture and setting it's ID's and save as ff7 model file.
- Test and correct all of those model parts by putting it over original files you unpacked and opening it's skeleton file(one that ends with **aa) in Kimera which you already have and probably noticed that it's best suited for such simple edits. Then pack it back to game and play with newly improved models.
Also make note that if you don't do all yourself, but just steal somebody's work aka "rip" the model for reusing in ff7 don't ask for any support regarding it in here. It's against the rules.
A little add to above to answer one other thing - you don't need to make new animations, skeletons nor anything else, just make sure your new model parts will be about same scale and position as old ones. One last thing - ff7 engine is pretty limited, your battle model can have at most 10 textures and also it's somewhat of an art to make it look nice as it's build from XX parts that aren't trully connected and can't deform - and no - you can't change that, soo even if you have greatest modelling skills end result will never be perfect.
Side not based on experience - althrough modelling usually is fun, converting and making battle model to look nice in game is boring and troublesome process(not counting weapons which are very fast and easy to convert and always look nice without any changes:P). Start from character you really want, as it's most likely you'll have enough of it after finishing just one=].