A K-1 effectively only adds 200 grams (the same weight as your FA50) to your standard kit, if you leave the K-3 at home.
It also adds larger files, especially in pixel shift that may slow your processing down. Do you need larger cards, or better PC?.
With your kit, I'd imagine you have enough bags so that's a plus.
The flip side to not getting one is, how are you going to make the nagging want go away?, just shooting film again only feeds it.
You might want to consider the K-1 + Prime only as a combination, keeping weight down.
if not, maybe get the 28-105 and lose the least used lenses to the cause.
Another consideration, would you still want APS-C once you have a K-1, if not you'll miss out on the 11-18 if that has any appeal.
All that change can work out expensive so start a spreadsheet on the combos and costs, with an eye to the eventual outcome, and then ask is it worth it?
The problem many of us face, is that even if the answer is no, that won't settle it if you really want one.
Put the replacement car off another year and the savings in depreciation on that car magically pays for the body.
Yeah, that did it