...and so it begins
I was in exactly your situation and with nearly the exact same ideas in mind. I did the manual circulation a couple of times and decided that a pump would reduce the effort and give me better temperature control.
1. Circulating with a pump while manually controlling the burner works, but it requires constant attention and it's a PIA having to frequently re-ignite the burner. Adding a pilot burner was a big improvement in convenience. http://www.pexsupply.com/Honeywell-Q...rner-4113000-p
2. The March, Little Giant or Chugger pumps would all work OK. You don't necessarily need to drill a hole in your kettle for the wort return. I simply use a wooden bar across the top of the kettle to hold a return manifold. Others drill a hole in the kettle lid. (I don't use a lid on my MT), and others still simply go up over the side with a length of tubing. Drilling a hole in my kettle did not appeal to me either.
3. I use a Johnson A419 digital temp controller to operate a solenoid gas valve on the burner. The controller probe is mounted at the pump outlet in the wort stream flow. Others have the probe mounted at the outlet of the kettle with a tee and a thermowell of some kind. I have a separate digital thermometer with the probe suspended in the grain bed. I adjust the controller according to this thermometer reading. I cannot claim that this configuration is the best way to do it, but it works for me.
4. Your last sentence pretty well describes what I wanted out of a system. It can be done and the cost isn't too bad, but by the time you get the pump, temperature controller, pilot burner, gas solenoid valve, liquid control valves, misc. plumbing hardware and hoses etc you will probably be looking at about $300 or so.
5. Lastly, it's not tremendously difficult to build and operate a direct fired RIMS, but neither is it the slam dunk that I thought it would be.