Simple Missing Weapon Tiers Fix

Corrects the lack of Advanced versions of the Eon, Equinox, Rattler, and Sidestar, without any additional balance changes or additions. Use this if you want to have those weapons be more viable for more levels without changing the overall framework of weapon balance in the game.

As far as compatibiilty is concerned, this won't work with any of the other available mods that correct this bug/oversight/odd design decision, but those also feature a larger scope. It should work on existing saves without any fuss since it doesn't massively rework the weapon tiers system.

Note: This is a prelude to a large scale equipment rebalance which will be coming Soon (tm). I just wanted to get something out which would be usable on existing saves before I get to work on the big one.