A potential system for handling balance of upgrade/downgrade costs without making all upgrades equal.

[Lurkily]

There's no reason that +50% damage and +25% damage should cost the same amount.  (The amount being one upgrade slot.)  Instead of purpose-building, it encourages broad-spectrum weapons, and the all-upgrades-are-equal model discourages the use of downgrades.

Instead of drones with a number of creative, purpose-built weapons, (My diggers, my long-range missiles, my close-in shotguns, my indiscriminate terrain obliterating grenades) you have more weapons seeking to use the BEST upgrades; and the most effective way to do that is to build weapons that are better at serving every purpose.  Even if that's not your goal, that's where you end up.

I suggest that every weapon have a certain number of upgrade points.  Let's say 12.  The most powerful upgrades should cost 4 points, as they do now; you get three badass upgrades.  But say you only want a digger?  Most upgrade trees only go out 5 or 6 tiers.  So the core energy upgrade (Tier 0) can cost one point, along with Tier 2.  Tier 2 and 3, 2 points, tier 4 and up, 3 points, and the last tier of any tree, four points.

Downgrades can make a more focused weapon, but they're still a downgrade.  They limit a weapon to a single task, even while they may improve that task,  I think they should provide a rebate.  But because higher-tiered downgrades aren't always more effective, higher tiers shouldn't grant higher rebates.  In fact, I suggest a single point for any downgrade.

This provides an incentive to focus your weapon's usefulness, and perhaps equip more types of weapon.  But it also doesn't incentivize you (as much) to take every downgrade available so you can take more and more upgrades.