Not all local allows cheater vent/s, and many only allows 1 cheater vent per structural and it is must be expose/not inside sealed wall. Not only that trap arms are allows to have an equivalent slope of its trap diameter ie. 1/4" per foot on a 1.5" trap/pipe would be 6' max, or 8' on a 2" trap/pipe.Of the two jobs, and depending on the location of the stack, walls that he can run lines through, etc., the plumbing is probably easier to handle than the tile. The only "hard" part of the plumbing will be knowing what meets code. i.e. in a new vanity, can he install a mechanical vent to save on running additional lines? Those sorts of questions. The supply lines - just about anyone can handle that if they have the right tools. I've said in a couple other threads, I've been sold on Pex, and thus far will only use the Wirsbo brand, because others have claimed it's easy to kink pex. I haven't had a kink in the Wirsbo. And, when I intentionally put a kink in it as part of a demonstration, the demonstrator took a torch to it, heated it until it was clear as glass, and it restored that section to the way it was before the kink was there.
I sort of take that back a little bit - depending on the layout - where the stack is, etc., his designs might be limited by the plumbing, particularly the drain lines - with the location of the toilet being the biggest question mark.
Most if not all PEX tubing can recover its shape if kinked (Wirsbo is the best of the class with recovery ratio of up to 98%, others are up to 84% and greater).
Anything can be done as long as there is enough room for the drainage to have it proper slope. And, vent is pretty simple as long as there is access to the roof or attic.