Really big congicus, or maybe a p. bichir bichir, although I highly doubt you'll get one of those. The cong might work though, as long as it is very large.
I don't think you want to keep a slender fish like a bichir with a rtc or tsn. Dinner time will come around sooner than you want it too. Plus, RTCs can get up to 4' long, and there isn't a bichir that can compete with that.
if you got a huge bichir it could work for a while but for life i'd say no both of those can et 5 feet and get atleast 4 so it could work for a while but not for ever
not to mention chances of seeing one of those large species of bichirs near their max recorded size is very small, let alone finding one and buying it. and in general growing one out will most likely not get you there.