I know you're trying to wrap this project up, but just to throw it out there, I would love to be able to work with dice pools in such a way to roll Deadlands dice: a skill roll is multiple dice, exploding per-die, highest single die or dice-explosion-chain being used to determine success or failure. I imagine the expression for this looking something like this: for a skill where you have 5d6, maybe it would be 5(d6!)L4. (The system that the old Deadlands eventually evolved into, Savage Worlds, uses a similar per-dice explosion picking the highest result, but only ever rolls one d6 "wild die" and one additional die of varying sidedness depending on the skill)
This presumably requires the sort of conditional operations on pools that you've tried to avoid, so I understand if it's beyond the scope of the program. As is, I can sort of fake it with stuff like d6! + d6! + d6! + d6! +d6! and the option toggled on to view individual pool results, then just ignoring the summed result and looking at the single biggest number returned. Mostly sufficient for real game use, just not perfectly ideal ;)