That's very true. Part of the problem is also that we are trying to use the old luxeon reflectors for the newer leds (Seouls, Crees and Rebels) and often, this doesn't work without some tweaking. I suspect the led manufacturers will carry on trying to make the best product they can and expect flashlight manufacturers to design around their leds. Kind of the same anguish I get whenever Intel/AMD change their pin-connections for their CPUs every few generations!
With it's 'lambertian' flux pattern, the Rebel is a pretty good match for the older Luxeon reflectors optically if you can get the Rebel mounted so it's optical axis is in the right position. In this regard the Rebel is less of a hassle than the CREE, which has a narrower pattern such that a lot of the light will miss some higher F-Ratio Reflectors that would work fine for the Luxeon or Rebel.
I have found some standard 20mm star boards that are set up for the Rebel, which will at least keep them properly centered, which solves the problem on two of the three 3D axises.
The remaining axis, which is still a problem, is HEIGHT. The older Luxeon devices had the emitter chip on top of a little pellet, where the Rebel emitter chip is on a tiny low profile surface mount pad.
If Lumiled won't mount the Rebel in a Luxeon star style package, some aftermarket company could easily mount the existing Rebel on a 20mm star board with a bump in the center high enough to create a nice raised mounting pad to lift the Rebel up just enough so it's emitter chip will be at the same height as the emitter chip on the older Luxeon III. With this type star mount the alignment would be correct on all three axises and you could just drop this star into any light that was working properly with the older luxeon star.
So it is possible, but I haven't yet seen such a height adjusted star.