Zip out floors would be great because they would make floor replacement easier after the inevitable abrasion, and allow use of the floor separately.
Trouble is that after alloy poles, zippers are probably the heaviest item in a tent. The "water resistant" zippers can be high quality, and are used by many companies on rainwear without leakage; however, they are quite heavier than the uncoated kind. In order to make the lightest durable tent, my solution to this issue has been to design floors to sew on after everything else with one continuous stitch line all the way around the tent border. Even with a faux lap fell seam, this requires only removal and replacement of two seams to replace the floor.
Zipper weight varies greatly, but my guess is that the 40 foot coated zipper, with stitching and pulls, will add at least a half pound to your shelter. I believe that is the reason many carry an ultra light weight under floor protecter that can also be used separately, as for example, when something is needed to go underneath a sleeping bag in a shelter. Some of the small tarp tent companies sell extremely light floor protecters.
Hope this is helpful.