Microcement on the floor would be rough.

You can polish regular concrete floors to a 200 grit for a honed finish. Water proof like a tub surround if, it's over wooden substrates. The cement overlay should be 3/8-1/2" thick. Rapid set Tru PC. This would give you a cream finish. Add sand for salt and pepper look. You can also, do a Terrazo floor

now they have a crawl space if i was to set up a jack system against the floor joist would that be a good soultion for the weight?

Concrete is porous. Water will saturate it and wick all the way across the house, rotting out everything in it's path that it touches. It can NOT be used in a wet area on a slab without treating it as the subfloor it is. For curbless on a slab, the whole shower area is cut out to be recessed. Then the mud mix creates the proper slope. Then it's waterproofed. Fully waterproofed. A liquid applied barrier like Hydroban is likely best. The whole bathroom floor. Not just the shower area. The walls too, with mesh tape at the join, and more waterproofing.

For a subfloor and joist system, to do curbless requires a dropped subfloor and joists, engineered correctly, and the same prep as above, just over the wood subfloor. Microcement is heavy, but not as heavey as genuine concrete, as it's just a micro layer, as the name implies.

Only after all of the waterpoofing can you do a microcement topping over the whole thing. This isn't a handyman or homeowner type job. It's super high end and very very expensive. It's even more expensive to do the cheap bad job and rot your house out.

I grateful for all this advice

Minardi ia totally correct just becuse a clent wants something does no always make it so. You can get concrete look 12 x24 tile no problem then you da as Minardi said

Update i discussed the situation with the customer. they were very understanding. we are now going to tile the floor. once again i appreciate all the advice and knowledge. thank you everyone!