I think that's pretty cool-- my only concern would be the roughness of normal gravel, and how I think that plant roots get less damaged (at initial planting) when using substrates like AS/Florabase. Incidentally, the damage caused to roots during planting is also why I'm a bit turned off by Flourite-- and being that Florabase can cause weird stuff, AS it is for me. XD

I think this is pretty cool though George, I'd just be careful in choosing the gravel to top it with. Maybe mix something with both large and small grains . . .

BTW-- can't be bothered with maintaining stem plants?