I don't think multipliers are that compatible with most forms of freshwater fishing, other than lure fishing. A few years back they were in vogue for pike fishing from boats, but this seems to be dying down now.
You could get all kinds of problems carping with them, assuming you leave the rod in the rests with the spool disengaged baitrunner-style, you could end up with one awful over-run if a fish bolted off.
The rod would be "upside down" in the rests and you'd have to use it "wrong-handed", ie right hand wind, if you went for reels without level winds, which are designed for distance casting.
The drags quickly get sticky if you don't remember to keep unscrewing them (be honmest, who does...?), no problem if you're using 80lbs braid lure fishing for pike, when you don't really let them have a lot of line, but I expect it could cause some heartbreak fishing for carp.