Simple Solution
Colonize where you can build and repair your machines. This is why Mars is the only place that makes near term sense. Rapid prototyping is also a technology being discussed for long term spaceflight that has commercial spin-off potential. Interplanetary travel and commersce will drive fusion rocket ptopulsion which is not the same as reactor design. In another note to your earlier comments on that, it was noted at the conference taht progressed stopped on fusion when every body decided to join together in ITER and spent years fighting over where to build it.Yet another shining example of why competition is bad and international cooperation is great.
Regards,
Mark