That's what I did on both my rafts. Switched the footbar for a AAA footbar so I used the old footbar as seat bar. The 60" wide footbar has more height as a seat bar than the 48" one did for my little boat - I think it was 7" vs 9" or so.
a bought a 10"x10" piece of 3/4" aluminum at Alreco for like $15 and sanded it smooth. Then I drilled four holes for two NRS Ubolts, along the middle of the plate. the ubolt nuts will protrude ant not allow a flat surface to mount a fishing seat, so you need to either cut spacer blocks from a HDPE cutting board or what I did was use a fishing seat quick release, which sits higher than the nuts, and allows you to take the seats off (I transport my frame on the roof, so being able to take the seats off is nice)
Attwood Release-A-Seat, Pedestals & Bases, Boat Seats, Boating : Cabela's
other good uses for an NRS footbar:
-the bend is the correct angle to make the bent arms that hold NRS floors. (getting the LoPros in the right spot was a bit tricky)
-you can cut one in half and make a rear fishing seat frame (the U turns in to two S's) - probably only a smaller boat unless you have a 72" or wider frame
-While we're on the subject of modding NRS parts, if you have the crappy one-sided lean bar that twists, and otherwise sucks, cut the last 18" or so off, add a LoPro like I did below. now you are leaning on the LoPro in an axis where it can't twist, so you are way more stable and hooked in.