I talked Scuds into coming with us so that's a 53MNK sorted.
I am worried though that Ritter and Flight are both too high at 56, as a 53-54party we could do crabs easy and catch up to them quick. 53-56 is too big a gap for the mobs we're thinking especially because our tank would be the lowest level in the party. It'll be messy, shit XP for all and lots of deaths for Ritter who's going to eat all our MP "tanking".
Look at it this way: at 56 you're at the low end of Colibri XP, remember they're still good at 60~. At 53 you are just way too low and better off on Kuftal crabs or something else.
Just my opinion, don't take it personally because I really want to have a proper LS party, but doing it arseways will just piss everyone off.