There are weapons called a falchion which are very similar to some forms of the scimitar, that are similar to a slightly longer version of the sabre. If that's what you're talking about, I see no problem with having it do a d8, and being finessable. At that point, you've merely refluffed the rapier. On the other hand, if you're talking about the hacking version of the falchion, which looks more like a machete, I wouldn't call it finessable.
As to two handed weapons, I don't think I'd allow one that's finessable. Perhaps I'd allow a hand-and-a-half weapon to be finessable though. Add some length to a sabre style scimitar like weapon, add a longer hilt, call it versatile, and have it do a d8/d10.
As to two handed weapons, I don't think I'd allow one that's finessable. Perhaps I'd allow a hand-and-a-half weapon to be finessable though. Add some length to a sabre style scimitar like weapon, add a longer hilt, call it versatile, and have it do a d8/d10.