First you need a base gun preferably in 9mm/Super or 10mm/.40 S&W because of the location of the ejector. Then slides in the base calibers you don't have...in your case Super and .45. Then you start adding barrels. As to who, just ask around to see if there is a good 1911 smith in your area...much better and probably cheaper than sending it off some where especially if the project is going to be done a little at a time.
From what I have read there is a way to modify either the .45 slide or the 10mm and Super slides so that the ejector doesn't have to be switched out when going to the .45. I had a Combat Commander at one point that had two slides that would shoot 9mm/Super and .45 ACP without changing the ejector on the frame.
You may be able to get most of the parts for your gun from RIA since you are starting with one for a base gun. And as you said, add a .22 Conversion and you are all set. As to .380 I am not sure if the magazines for 9mm will handle the feeding of .380....
Possible calibers:
.22 LR
.22 TCM
.30 Luger
7.62x25mm (rounds must be slightly shortened to fit into the mag)
9mm
9x21
9x23 Largo
9x23 Winchester
.38 Super
.40 S&W
10mm
.400 CorBon
.40 Super
.357 SIG (unsolved as of yet feeding problems)
.45 ACP
.45 Super
.460 Roland
.45 Detonics Magnum
...just takes money....
Bob
