If you aren't re-winding you can probably cut them off without changing performance significantly. They are handy to have if you are re-winding as they keep the wires from popping while you wind. They might not be highly electrive conductve, If they aren't you can just leave them there. If they are magnetic core (ferromagnetic) they they are actually performing work by directing the flux of the coils to the ends of the magnets, increasing the power of your motor. It is hard to say what value they are actually providing / sacrificing without looking at it.
Rotor Flux ring Thickness
A Neo42 magnet generally has a Br of around 0.95 Tesla, and Iron saturates at 2 Tesla.
Tesla is a unit of Flux Density, and since half your flux travels between magnet poles (1/2 goes to the magnet to the right, 1/2 goes to the magnet to the left) you want about the flux ring thickness to be about 1/4 the width of your magnet pole. (1/2 flux in something that can handle 2x the flux density = 1/4 the cross section)
Since you have 2 magnets making each pole, you want your flux ring to be about 1/2 the width of one of your magnets. I haven't read your thread that carefully, but it looks like your magnets are about 12mm wide, so you want about 6mm of flux ring. One way to tell if you have enough is to put a piece of iron on the outside of the flux ring, it should have almost no attractive force if you are at saturation, and no attractive force if you have more iron than that. A good design should have just a little more iron than saturation.
Also you mentioned that I said that Neo42 has higher temp ratings, and that isn't entirely accurate. High temperature Neo 42 has higher temp ratings than Neo52 or other high MGOe magnets. As you get higher temp ratings, your maximum energy Product (MGOe, i.e 42, 48, or 52 ) decreases, so you simply can't get Neo52 with higher than 80C ratings. You can still get Neo 42 with 80C temp ratings, but you can also get Neo42 with 150C Temp ratings, you have to be sure you get the high temp rating stuff if that is what you want (and I hope it is).