When dealing with storytelling and writing, one of the fun exercises I like to run through is something I call Turn That Around. It comes out of something Ridley Scott talked about having picked up from Stanley Kubrick: when you are confronted with something where you have an automatic "oh, I'd do that" response, you stop and ask yourself: What happens when we turn that around?
The first time I heard Scott talk about this was re: Blade Runner, when they were assembling the opening sequence where Leon shoots Holden under the table during the V-K test. Scott was uneasy about just showing a regular shooting with a regular gun, and toyed with the idea of the gun behaving differently. Maybe it didn't shoot bullets but instead caused the target to implode, he theorized. The idea ultimately never went anywhere, and so for various reasons (most of them budget and time) they just went with a more conventional gun-that-shoots-bullets approach. (I wondered if he had been thinking, however distantly, of the striking-looking "gas gun" that was featured in Logan's Run.) The idea itself might not have gone anywhere, but the impulse to not take on face value ideas that come automatically to mind stuck with him.
It's a good habit to get into — as long as you're using it to break the ice of habitual thinking and not using it to overturn a way of doing things that exists for a very good reason. If you break a rule, you have to replace it with something at least as good or better. Science is the same way: no junking a theory unless your new one encompasses the old.
So, no, I don't think Blade Runner would have been better off with Deckard firing a "black hole gun". That would have been like putting a fringed doily on the hood of a racecar.