would a Beis Hillel talmid suggest a tzaras habas as a shidduch for a Bais Shammai talmid?
Absolutely! Why not? According to both B”Sh and B”H it is 100% mutar for talmid of B”Sh to marry a tzaras habas. (before it formalized to allways follow B”H, after which the above stament is no longer true)
In your view you have an interesting paradox and a pretty good riddle:
How can you be oiver lifeni issur by helping someone do somehthing muttar?