And no you can't use the nagants skeleton and animations. The Webley is a top break revolver. Meaning you "break" the barrel forward. This also automatically ejects all the cartridges. So it would be like trying to use TT-33 animations for the C96.
Clearly you have never tried making new weapon.
First, nothing stops you from using any weapon skeleton, the only question is amount of bones and their hierarchy. You can even make AT rifle with nagant skeleton, with totally changed animations.
Second, just only different reload animation doesnt make all other animations useless. If in regular nagant animations webley fits normally in right hand, then it can use nagant animations without any problem, you will just need to add few different reload animations.
Making c96 in TT animations is totally possible, unless standart position of hand does not match the form of C96 handle. You just need new reload animations, probably new shot animations.
Remaking whole skeleton and whole animset just because of different reload is probably one of the most pointless and giant waste of time and work you can ever do in RO2 modding. Especially because due to cover system every weapon in RO2 has A LOT of animations, about 70 for SMG for example, even more for bolt action rifle. Not much different for pistols and revolvers. Remaking all of it would take RIDICULOUS amount of time.
G43 has different reload animations from SVT-40, that doesnt mean that we had to remake whole skeleton and whole animset, we only added new reload animations to SVT animset.
G98 has different bolt handle position, it doesnt mean that we had to remake the whole animset. We only changed reload and bolting animations (quite easilly).