As you guys are allowing the player to remove/extract gems, i think it would be really cool if you could randomly find a weapon that already comes with a gem on it. Not only it would be a potentially exciting reward, but it might help make Finley have much more relevant and interesting deals.
Finding a weapon with a nice gem might help encourage people to try out different weapons, specially when someone is unwilling/afraid to spend gems on weapons they dont consider ideal, or too attached to their current weapon that already has gems.
If the player is allowed to destroy a weapon to extract a gem, like you can do with runes, then that opens up so many possibilities. Maybe weapons with a small chance of having gems on them could be a more interesting substitute for simply increasing the droprate of gems. Maybe Finley could have weapons with gems on them, so his wares would be significantly more interesting, contrary to now where many people dont seem to be very fond of his stock.
And its just so likely to be satisfying in general, as its basically putting two/three potentially great rewards in one drop!! Maybe you really like the weapon, maybe you really wanted the gem, maybe both are a perfect match