With the Milwaukee you can. That's the whole idea is they draw you into buying $250 12.0 batteries, but they fit the drill, impact, sawzall, weed eater, mower, bandsaw, etc. I'm sure it runs fine off the 6.0 & 8.0 with a shorter run time. Power will go down with standard batteries vs the HD just like every other tool.
I'll probably buy one once my old gas mower dies, but I already have over $10k in tools and batteries so for me it's convenient to keep going with the same batteries.
Considering I already have stuff like the super-hawg that pretty much requires a 8 or 12ah battery to be useful, I see no reason it wouldn't work out just fine.
I'm honestly surprised they didn't use the fuel mx, because then idiots like me would buy them and then need a few light plants and a jackhammer since we have a battery for it