That one foot high of space under the coop seems like a good idea until the hens choose to lay their eggs under there. It's no fun fishing out potentially bad eggs with a gravel rake because someone made a "secret" nest. If you put hardware cloth around the bottom of the coop to the ground to enclose that area, put it in a picture frame or something to make the panels removable so you can fetch out injured/sick chickens or eggs if/when needed. They will always find the hardest to access spot and that's where they'll be.
Honestly, I'd consider avoiding the under coop space and get less chickens. Bantam vs. Standard - if you're concerned about egg production I'd suggest white leghorns - maximum size eggs every day with a minimum hen body size, but not quite as small as bantams. Bantams lay smaller eggs than standard large fowl chickens, and they may not lay as often. White leghorns are quite a bit smaller compared to heritage breed chickens (both heritage breeds and white leghorns are large fowl chickens). Only downside is I've found White Leghorns can bully/feather eat quite a bit the non-white-leghorn chickens, so a mixed flock may not be the best choice, but it may just be my individuals.
Also consider quail instead, as they can provide both eggs and meat with rapid turnaround, and do well inside dwellings or sheds with the proper setup.