Alter the mining area... That actually seems like a really neat idea, there are all kinds of effects you could use. I have the urge to say "and they could plant mines!", but given the play style that could get confusing, heh. Well, unless maybe the mines had a red beacon on them and forced the player to drill 4 tiles around them first to disarm them or take damage or something. Oh, or to disarm them before they explode and damage the player.
Battery overflow damage seems like an ok idea,but would probably only come into play with the power amplifiers that double energy gained. If weapons like the larger cannon need 2 energy and the battery can output only one, or you have uneven total power then that can also make things interesting. Not being able to see your inventory on screen is also an interesting issue, I imagine it like setting up a circuit board before each match and then playing with the results. In backpack hero though, you can choose to move items around in your inventory at the cost of your turn, or each inventory action could be seen as a tick/mining block for the enemies. So, you could potentially swap out the mining area for the inventory temporarily if the player chooses to in a given round to make adjustments if they want. But the general play would encourage setup beforehand.
The items effects are an interesting aspect which encourages the need for management, there are all kinds of interactions CR-8 has between their items, use of empty space or full space, rows of items, alignment, various reactors even, etc. Makes for quasi circuit design, heh.