Yeah. It's frustrating to have to choose between throwing mods on ordinary weapons/armor and possibly running into something you'd *much* rather spend the mods on or lugging around a ton of mods in hopes of an advanced weapon. I figure the only way to bridge this gap is to either to do this or maybe something waaaaaaaay nuttier (like say enabling you to turn an ordinary weapon into an advanced weapon with enough extra parts). The last suggestion for this was considered too overpowered in its original form, and I think it likely was because the responder believed you'd get all the mods invested in a weapon back, enabling stuff like dragging around an otherwise useless advanced shotgun stuffed with mods while waiting for something else, then should that something else show up taking to the shotty like a piñata and snatching up all twelve tasty mods (awesome for the lucky punk, terrible for the game balance). The limit on how many mods you get back is an attempt to stomp that vision flat.
EDIT: By the by, this is sort of how I've later envisioned a possible way salvage could work behind the scenes - each mod on a weapon that gets salvaged adds 0.25 to the counter; every 1 point on the counter adds up to a guaranteed mod, and the fraction left over determines the chance you get an extra mod. So for example, if you put seven mods on an advanced shotty, but later get an advanced combat shotty, when you salvage the advanced shotty you are definitely going to get one mod and have a 75% chance to get a second. I think this method could also make it easy to tweak the numbers if it's agreed that salvage needs improvement (and since this *will* make balance different, I think it makes sense to be a bit conservative about this).
Thinking on it, there's a decent case for tweaking this into a master trait (it requires an advanced trait already thematically and power-wise, and it could *maybe* stand to be improved for the people who don't think they're getting enough extra mods out of it).