Joe Same, tacticool is cool, but vanilla just have a bit different feel, which sometimes I enjoy more.
Re left hand mod (This one?
https://www.systemshock.org/index.php?topic=9436.0 ) I assume it's simply a hand model added to all of the weapon models, so in current state it's not compatible, I mean you can use them together but my shotgun will not have a hand attached to it.
Adding hand is not so hard really, it can be borrowed from the left-hand mod itself, but I got so annoyed working on this one that I don't want to even open blender for some time, so don't count on it. Also, I think the idea of the original that there's this lil module attached to the pump handle that automates pump-action so you don't actually have to use your left hand at all (possibly originally as a justification for using thief animations on hybrids and/or not making the left hand), so from that point of view adding a left hand to a shotgun doesn't make a lot of sense.
And re remaking pistol - that might be possible, I might have a mood to do some modelling again in the following few months, but on the other hand, I might also finish my playthrough at that time, so again, don't count on that too much.
Also, there's a shading issue with moving parts of guns, you can see it on the tacticool pistol model as well, it's like tringular-ish looking shadow spots appearing in some lighting conditions on the pistol slide, it will get worse on a more complicated model, and I don't even know if it's fixable or just an engine quirk (will appreciate if someone actually knows an answer to this). So until I know that this issue can be avoided - I'll def not even think about doing pistol, otherwise, it'll be a lot and a lot of hours of tweaking things around and praying that this 100ish time shading will be bearable.