It has been done in French mods (they have some ideas but their programation skills are not incredible, so there are many many bugs compared to CE).
The problem of adding new clans is on the backround. If you're Camarilla, and find a Lasombra (or any other non Camarilla clan member) Embracing, There is no trial, you kill them both and that's all (like the poor Sabbat guy you kill in the tutorial). There are exceptions, Camarilla Lasombra do exist, but they are not even considered as kindred (I mean that if they make any mistake... and even Nines will not stand up to save a traitor's childe ^^).
Camarilla Tzimisce do not exist, but Camarilla Assamites, Ravnos, and Sethites exist (at some extend). Giovanni do not have Camarilla members, but they can have some arrangements with the Prince/Primogen of one particular city, so they can stay. They can ask to the Prince for the right to embrace, but usually if they do not follow Camarilla rules, they are kicked out, not killed.
If the sire has an "important" reputation in the Camarilla, even if she is not a member of the initial 7 clans, maybe the childe can survive.. But instead of being killed, I'd imagine the sire would be kicked out (because of her reputation).
Lasombra's Obtenebration is a mix between Protean and Obfuscate. Ravnos' discipline could be like Dementation. Giovanni's Necromancy is just a fancy Thaumaturgy. Assamite's Quietus is very close to Thaumaturgy (blood path of course) as well. Sethite's Serpentis is just a fancy Protean.
We need a new game ! ^^