Drilling holes in joists is done. Has been described here recently. Someone will post a link soon.Originally Posted by hans_idle
Moving drains by 24" means you have to recalculate distances and ensure there is enough venting in the pipes in relation to distance to stack and pipe diameter.
Can't do the elbows above the floor... why, because of venting, except if venting (e.g. by an AAV) provided. Just background information, not a recommendation.
Elbows to use, assuming you can simply lengthen your drain pipe branches and arms, will be the long sweep kind; they have a large radius of curvature. Or two 1/8th bends (two 45 degree angle turns). Not the tight elbows, which are only for air in venting pipes, up high.
Cabinets will be fine because the weight of a piece of granite is less than or similar to the weight of a tub of water. Check this anyway, regardless of my saying it'll be OK.
NJ code? Don't know.
Tankless? Electric? Noisy.
May still be a good plan to install the valve and Tee.