@Christopher B. Thanks for comments and your post! You have some really good questions and I will try to respond as best as possible. First, a good thing to always remember when reading things on BP or getting advice in general is real estate is like politics, everything is local. I.E. my note about the post being based on doing deals in Texas. What works in Houston or Texas may not be exactly applicable in Dallas or Knoxville. State and local laws can vary drastically.
The same contrasts came be found when comparing laws and regs governing real estate licenses, transactions, etc. I have heard many gurus and seminars pitching programs which might work perfectly in their own backyard, but are illegal or not practical in other parts of the country. Make sure you are getting advice from those who know your market.
Case in point is your question about being licensed as a GC. The state of Texas requires specialty trades to be licensed, but not general contractors. But, certain cities within Texas have had their own requirements for GC's above any minimum standards set by the state. So, my answer to the first question would be no, an investor does not have to be licensed as a GC in Texas to do their own rehabs.
Our company provides PM services as well being a general contractor. We are not licensed, but would be if laws changed. We do carry separate insurance policies for each. When we PM a project we advise the client to get coverage which protects them accordingly. In answer to your question about permits, we pull permits in the name of the investor listing us as a contact on the permit as well. Mechanical permits are pulled under the master project number. Permitting gives contractors control of the project and I have seen bad contractors use that control to the disadvantage of the investor,
Regarding your last few comments about crews, a good PM should have crews relieving the investor of that problem. If your PM doesn't have crews available to them within a reasonable lead time I would question why not. It sounds though like your are considering starting your own construction business which is somewhat outside the scope of the post. If you have enough volume on your own or through other avenues then it probably makes sense. My post was focused more on the part-time or lower volume investor who is active, but not active enough to justify a full fledged construction business while understanding the advantages of using a PM.
What you might consider is expanding your business by partnering with someone who is already in construction or providing project management services. It may reduce your risk while allowing you to build your business even quicker. This brings up another point about the stories you hear about getting rich in real estate. None of them did it alone.
I hope the above helps and good luck in your business!