True. I have fired lightweight .45s. They HURT. The recoil is harsh.
Even so, I could put up with occasional practice with a very small, very light, .45.
For revolver fans (there is nothing like a good revolver) the .44 special would be a good starting point.
The problem I have with modern firearms is that they are all over-engineered, and thus they are too big for their cartridges and too heavy and too big to fit in a pocket.
This is, in my thinking, probably because of too many lawyers.
How many firearms are now produced with a "liability trigger" of 15 or 20 foot-pounds or more?
To get back to the 'ThunderZap', well, I hope that the engineers will get it done.
I don't know how small and how light you are thinking of, but the EAA Witness Polymer Compact in .45 ACP is a joy to shoot. It has a ported barrel and produces less *felt* recoil than my 1911A1. Kind of hard on your night vision maybe, but I've never shot it in the dark, so I don't know for certain. Doesn't seem all that bad in a low light indoor range.