Holographic bullets aren’t really ballistic. The borg might have been able to adapt. Though if they were fooled by holograms and force fields, an anti-borg program could have been made that makes them get stuck in an endless non-euclidean maze (and I mean one of the interesting non-euclidean spaces) or just tear them apart by having dozens of force fields pop up through their bodies.

With all of the hologram projectors they had in Voyager, not to mention the portable one, they really didn’t explore the tactical advantages they could give. You could literally make any boarding party believe they had transported to hell, or let them run around thinking they are winning and took over the ship when they are actually just standing around in the brig–or airlock.

Or have them board only to hear “warp core damage critical, breach in zero point–” then give them some kind of afterlife sequence where they settle into their new afterlife and pass time telling each other about state secrets they were privy to, now that it doesn’t matter anymore.

It’s kinda funny that they had holograms but didn’t really ever explore any post-facts kind of themes, other than using holograms on less advanced species.