Re: A Good Frame???
Since you have everything to put on it a good vintage frame would be my choice. A cruiser frame from the thirties to fifties will work well and I know that my 63 Schwinn middleweights (Americans) have frames every bit as heavy and I was able to mount heavy duty 2.125 wheels with no problem. Using the middleweight fenders was a little dicey and I had to do some small modifications to them to fit, but the results are nice. I can't speak for middleweights of other makes. It depends on what you want, of course. I think a strong frame is a good starting point on any build.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...