Hmm, while the article is interesting, I'm guessing I don't read the same kind of SF and fantasy as the author does or something. Aside from computer game fantasy, which obviously has this incentive to be creating an endless variety of visually cool weapons that are increasingly powerful as the game progresses, most of the fantasy I read has swords, bows, axes, spears, crossbows, knives, or gunpowder weapons if it's in a more recent time period. There may be wands, magical staves, or enchanted weapons, but it's pretty short on bizarre and highly specialized weapons.
Likewise, with SF, there are various kinds of "laser" or "disruptors" or "blasters" that are similar to modern pistols and rifles, and of course weapons mounted on ships. Actually, if anything makes me suspend disbelief it's the fact that they have this technology to make futuristic guns that don't seem all that more deadly or accurate (or better at non-lethally subduing enemies) than what we have now.
A couple of nits:
Instead of creating a crossbow that fires arrows and bombs and uses a backup pistol embedded in the design, stick to a dedicated weapon that can do a single thing well. Give the character a separate backup pistol instead of building it into the crossbow.
Do any SF or F authors do this, except in video games? I haven't read any.
Why would a character carry both a crossbow and a firearm? If gunpowder is available in the setting, why rely on outdated technology?
Because the use of those technologies actually did overlap for quite a long time in history. Early firearms were an improvement in some ways, but it took a while to perfect the technology to the point where they were
always preferable (and easier to use) to crossbows and melee weapons.