I believe you’re thinking of inverters (DC->AC), not of rectifiers (AC->DC). That’s actually the beauty of FF, because you already get a inverter for free. Output capacitors are already required, otherwise you’re getting only impulses of a few milliseconds.
Or are you’re thinking of eliminating those output capacitors? And replacing them with what? Inductors of the same size? Not much gained (but might be cheaper).
I’m thinking of computerized control circuit which switches the several capacitors onto the grid depending on demand and circuit phase. You still need an inductor for leveling out the edges, but you need them anyway. So it’s an computerized inverter. I think the modern ones are computerized anyway.
You can compare this to modern automobiles with their computerized ignition systems compared to primitive distributors in cars twenty and more years ago.
Or if it’s of Rematog’s big-scale utility (200 FF generators), you might orchestrate them to output something that looks like a sine wave. You then don’t even have something with a stable frequency, it’ll look much more like you’re Windows Task Manager with two processor cores running on 50% speed (because the process running is only built for one processor). The load jitters between them two.