So after playing far too many hours in the last few days, I've identified some issues that I think may be solvable, but probably not with just modding.
The Issues
So what are the problems? They aren't game breaking, but I think they reduces the options, richness, flavor, and flow of the game.
Basic Loot
This is the coins, health, missiles, and other random stuff you get from breaking containers. There are two main issues: 1) There isn't enough variety, 2) I don't care what drops, whatever it is I'm going to pick it up anyway, no need to even look as I zoom past.
Shields
They are awesome, but we are capped at two. Which is good, because they are awesome. But that feels bad when you get a combo that should give you 3 shields. Also, they are pretty damn awesome, which is concerning.
Energy
Since you get it back every room (even re-entering rooms), often you start clearing a room with your energy weapon, use it until it's empty, and then finish everything remaining off. Sometimes you save it (Guardian Blaster) to deal with a specific enemy, but most of the time you can just go to town right out of the door. This tends to constrain the energy weapon to the start of each room, and makes tactical choices about using it less interesting.
The Solutions
So what would I change to improve things?
Part 1: Energy, Power Ain't Cheap
First, energy is ONLY awarded when clearing a room once, not every time you enter a room. That's not going to impact most people, but it opens up a bunch of other options. So next, let's cut out the free unlimited refills and give the mechs an energy regen stat. It may be pretty high, 50 or so for the white mech, but it not only adds a new stat to customize for each mech, but gives us a stat that can be changed with drops (more drops!). Now that we might not always be topped off, adding energy tanks that drop from containers and enemies is much more meaningful, and helps with the issue of energy being so front-loaded now that you can get more energy mid-clear on a room.
But energy tanks have a lot of potentional. So instead of just being mindless +x energy pick-ups (which would still be a great improvement), they now function as reserve tanks for which most mechs can hold only one (bonus, another stat on mechs to customize or change with drops). Whenever you pick up a reserve tank, it attempts to refill your energy bar. If it would overfill it, you instead keep it and it automatically refills your reserve bar if you try and use your energy weapon when you don't have enough energy to fire (UI side-note: It would be great if our energy bar UI and the shot count = 0 should turn red when you cannot fire another shot, same for missiles). To accommodate multiple sizes of reserve tanks, if you have one already and walk over another, you keep the largest one, possibly adding the smaller one to your energy bar if it will all fit, otherwise dropping it to the floor in case you need it later.
So we've got new drops, mech stats, and a new mechanic involving stocking up on the largest reserve tank for that room you really need to go crazy in.
Difficulty Very Easy: x2 energy regen stat
Difficulty Easy: x1.5 energy regen stat
Part 2: Shields, Some Conditions May Apply
In order to have more shields, they need a tiny limitation. Part of this limitation will relate to energy. First, you only get shields back when you clear a room for the first time, just like energy. Second, you only get one shield back per room, even if you are missing more. Third, if you get a shield back after clearing a room, you only get 50% of your energy regen stat back for the clear. So now 3+ shields are more reasonable. But we aren't done yet...we can add a new reasonably rare pick-up that restores one shield point.
Speaking of loot, to make players think more about look. New EMP proximity mine "pick-ups", which are a bad thing. These are proximity mines that ONLY take out a shield point of any nearby mech. They also only exploded if you come near, making it nearly impossible to dash in-and-out without getting hit. Normally you clear the room so they auto-explode, but they can be detonated with missiles, if you really need to get by. This now means clearing containers mid-fight can add obstacles. If a room is already cleared, an EMP mine explodes as soon as dropped, so it is only dangerous if you are clearing containers up close. Remember though, EMP can't take away health so they can't ever kill you. On the plus side, EMP mines also destroy all shots when they trigger and stun enemy ships, so they've got that going for them.
Difficulty Very Easy: You get all your shields back and no energy hit.
Difficulty Easy: You get onyl one shield back, but no energy hit.
Difficulty Hard+: EMP mines take out all shields, not just one.
Conclusion
So we've added two mech stats (energy regen, reserve tank capacity), five basic loot drops (small reserve tank +20, medium reserve tank +50, large reserve tank +80, shield recharger, and emp mine), multiple possible power-up drops involving energy regen and reserve tank capacity, not to mention reserve tank efficiency (get +20% energy from reserve tanks). And also made energy weapons more interesting and flexible, along with giving a lot more room to the design space for shields.
