Dave, why do you think it won't help at all in a SFBD?
IMO, a table of any sort would help, especially if the floor is uneven...
Now, if you are simply grafting your new frame into the insides of the existing frame, I can see where one can get away without the table...
however, if you are grafting completely new frame rails all the way back, from the point where the frame curves upward at the firewall (aka, only using front frame clip), wouldn't the frame table be extremely helpful?
If all goes well, I will start a SFBD project on my daily this winter... I have another front frame clip, so I can build the frame and suspension, while still driving the daily...
I am toying with the idea of building a modular frame table that can be dissassembled into smaller bench style tables. 4 sections that bolt together and each have 4 adjustable legs to level the thing out.