I used to play with bike carbs back in the mid 90s with bike carbs
and many guys like yourselves have played with bike efi units which
most know are super cheap vs jenvey units.
If you can use the bike efi quads and twin x 2 then thats the way
to go to save overall costs.
A cnc manifold doesnt really make sense but flanges do for most of us.
There are twin cylinder engines with efi that could lend themselves
better for a compact flange to use those units as well but forgot the bikes.