I want to make my own breaker box to be used as a sub panel. ...
Am I missing anything, is there any NEC reason I can't do this?
...I need to add some controls for a 7-1/2hp dust collector, a starter and an estop and a couple of switches. I don't see any code reason I can't add this stuff into this panel. ...
Assumption: You are not part of a NRTL panel shop (UL508A for example)
First: Does your state require listed equipment? If you get by that, then -
Your AHJ should consider this an industrial control panel. NEC 409 applies. If so, there are marking requirements - including an SCC rating.
There have been a few threads, where posters knowledgable about their AHJ, have said clearly, 'no panel build per NEC 409 would ever be allowed in their state' (parqaphrased).
IMO, nothing you can't do, just have to follow the code.
ice