The way Unlagged works, is to "rewind" the server whenever a player tells they wanted to shoot. This is created based on the idea behind Counterstrike.

Primary fire is Unlagged shot, Secondary fire is Lagged shot.
There is also a console command Lag milliseconds -> Lag 300 . This allows you to adjust your ping to something more normal, like if you are normally not playing Unlagged with a 70ms ping, you can do Lag 70 and you should get ~70ms worth of lag.

Adding in the other hitscan weapons should be no big problem, but a lot of code needs to be done, atleast for the shock rifle and combo.

UTPureRC6+ already does what it can to minimize network traffic (from uscript).

You could make an Unlagged/ZP mix, but I think a better solution is attempting to make a more solid Unlagged. Unlagged has some issues, like with warps or large player speeds, as it uses Interpolation and Extrapolation to try to get a perfect position of players. This can be in some cases be problematic, but it tries to solve it best possible. Also Unlagged makes the server quite unreliant on Tickrate (due to the Interpolation).