What is your opinion of screwing lath to drywall suspension grid, the type for attaching drywall to. Would you be worried about cracking?

Please don't ever do this

I have heard of bad failures from someone putting metal lath and plaster on drywall grid.

It is OK to screw metal lath to hat channel wire tied to 1-1/2 channel iron. I have doe this with good results.

The preferrable method is to tie metal lath on 3/4 channel iron. Channel iron reinforces the plaster. I'll post pictures when I pull them up. We are starting a decorative plaster ceiling just this week using 3/4" iron.

I heard of someone who put metal lath and plaster on drywall grid and had terrible cracking. When they filled in the cracks with caulking, the ceiling cracked worse. You can tell by the amount of defection that a ceiling like this is doomed to fail.

BTW, when we frame ceilings we space the iron 12" O.C. I worked for a company years ago that did this and I have done it ever since. These days they only make light fixture for 16" O.C., so the lights may need to be cut or reworked.