Don't fear the chainstay mounted brakes. They are perfectly fine for the purpose the OP seeks. If you are going to be slogging through the mud, then avoid them. but if you are going to be doing that you should probably avoid a vintage MTB in general.
I am not a big fan of V-Brakes. It seems to me in order for them to stop well, the pad has to be very close to the rim and if the rim gets slightly out of true it rubs.