When we discovered we were going to need a protection paladin for Felmyst (From PTR reports), we just spent a couple weeks, and forced any unneeded tier gear/tank gear to a holy paladin. By the time we got to her, we had created this monster:
WoW Armory Light v0.5.2 ALPHA minus the belt, which was picked up after our first kill. As has been said several times, there is no reason to not have a protection paladin on this fight.
Once you're approaching Felmyst, you will likely have several tokens that people are picking up for secondary gear. If it's really tight, you can ask your raiders to hold off on a piece or two if it's a massive upgrade for the tank suit.
Edit: Another note, we originally kited our green beams far away from the raid for our first two kills. We then swapped to SK Gaming's phase 2 strategy, and it worked wonders for solidifying threat. It involves kiting the beam in a consecrate sized circle with the paladin standing in the middle, but you'd be best off watching their kill video for illustration.