[Tuning: A way to make time invested in a weapon pay off]

The other side of it being, that I do like this idea immensely as well.  With what Marshmellory proposes however, while still doable on Draco, perhaps make certain areas weaker for Tuning than others.  Ones popular with all the Tenno wouldn't give much variety to the worlds you've built.  Heck, you could even make Tuning Drops with special missions-  You want +5% damage or Fire Rate?  Do a Tower 3 Survival with the equipped weapon and kills with said weapon you intend to Tune.

It would give a chance to make stronger weapons further stronger, it would also allow those who want to keep their older weapons that aren't as strong, have fun with them again.