Crazy Glock idea?

Not really sure about the laser, they do have benefits though.
A long slide 45acp would benefit from the typical things that come with a longer barrel (accuracy, velocity, sight radius). Not sure if it would make a good CC pistol due to the longer slide and barrel, but that is a personal preference. I know one gentleman that carries a G17L without any complaints.
Your G20 may benefit more from the increase in barrel length due to the 10mm cartridge and its large load versatility.

I see no use in butchering a perfectly good G20, which fires a superior cartridge with higher mag capacity. If you want to create a tacticool .45 to accessorize for fun, that's a different story... but "practical" it is not.

Naw, that isn't butchering, just accessorizing. Adding a second upper would be a pretty interesting idea, especially if you already shoot any .45.

For pure home defense, and don't take this as a knock on the J Point because I have no experience with them, but I don't think that the added complexity or possible lower durability of a red dot sight over iron sights would make any difference, since they don't need to resist being banged around on your hip all the time. And if you shoot it faster and better, go for it.

I also agree that the 10mm will probably see a bigger gain from a 6" barrel than a .45, but either way it's still a pistol and having two different calibers for your 20 would let you shoot it more, and differently.

If I got the idea to do it, I probably would.

That picture makes me want one.

I just meant that I don't know anything about red dots on pistols, and I don't know anything about the J-Point or any other red dots. If a red dot makes shooting easier for you, and it seems to for many people, go for it.

Butchering or not, it still screams "ninja" to me.