Way to make higher tier weapons feel more "worth it"

I'm not a game dev, I have no idea how to balance a sandbox like this. But here's an idea.

White weapons are stuck at level 1. So, no more stitcher 4. No upgrades available. They are what they are.

Greens can only be upgraded to level 2.

Blues can be uprgraded to level 3

Purples can be upgraded to level 4.

You SHOULD be at a disadvantage fighting someone with a Bobcat when you've got a stitcher in their optimal ranges.

It would still allow lower tier weapons to be serviceable when you're first getting started and encourage you to find and use upgrade.

But loading your stash with EASILY replaceable stitcher/ferro 4's no longer is possible.

Again, I'm not a dev. But the need to get actual weapon upgrades feels essentially non existent when the first tier of weapons can be very easily and cheaply upgraded to be arguable better than any pink weapon in the game.