I agree pretty much completely with the above post. Having more than two alignments allows for more of a collection game, but just holy vs. occult would probably be more fun. I was really just spitballing, anyway.
I do think holy shouldn't be intrinsically better than occult--rather, it should be safer, but have less power to compensate. Or perhaps holy items could only be used by pure characters--who would generally be newbies--while occult items are equal, but can be used by anyone AND advance their user's corruption. That would work well with our balancing system, no?
One thing that could be interesting would be (like in dark souls, kinda) temporary effect you could add to a weapon, like 'oil of +2 fire damage' that only last for a single battle/x turns. You could upgrade these oils or combine them for special effects, but they're a limited resource, so you'd have to make hard decisions about when to use them or whether or not to combine them, and gives a constant feeling of scarcity and being pressured. And make it take time to combine them and apply them (and maybe certain rolls?), so you'd have to plan for encounters, and anticipating badly can be disastrous.
For people who hate these kind of decisions, maybe make it also possible to just straight up upgrade your weapons, but make that be much less cost effective (in a power per credit way) so again it comes down to making meaningful choices.
And do not let players tinker anything that they aren't going to use by themselves. Otherwise we end up in our latest state of tinker where Armory is full of player made items that nobody has ever used or purchased. The "get royalties" idea gave tinkerers entirely wrong kind of incentive. Make them pay for parts.
Yeah, depending on how things work with npc's, we'd have to think long and hard how to handle how to handle that side of tinkering. If we indeed go with something not being mass produced, but instead having to pay an npc to build it for you if you can't do it yourself (being less money efficient) you could still give the inventor some sort of bonus to building it (though perhaps only for a limited time?). If we go with the holyness level thing, perhaps the original inventor grants a little holyness bonus to anything he makes that he himself invented.
Also, whatever the currency ends up being, maybe make it so the smallest amount of money is worth much less than 1 token currently is (like, make standard mission pay something like 50 to 500 credits). This allows more granularity and makes it easier to pay other players for small favors (should stimulate inter-player economy), and leaves more room for haggling.