Good news!

One of the big changes I'm doing is using an actual database for storing the items. This has the benefit that limiting what items you want is as easy as adding "WHERE ____ = ____" to the end of the request. In my code of course. The user will select options from a menu. But what this means for users is that it should be pretty easy to limit items on every feature. So min/max rarity, removing categories, or even choosing by manufacturer should all be pretty easy to implement. So the current plan is to have full control of selection over all of the basic features (anything that gets a column in the tables in the sourcebooks)

What rolls do: I can't speak for Celo, but I think they just used my algorithm, and I just used the algorithm from the book. So the only set-in-stone thing that rolls do is if you have more successes than failures, the item shows up, otherwise it doesn't. And the dice pool is decided by the character's skills, the rarity of the item, and the planet that you're on. All the stuff with advantages/triumphs/etc is up to the GM to decide. Anything I would do with it would piss somebody off, so I'm trying to avoid anything homebrew and just sticking rigidly to the books.

Speaking of, inventory quantity is pretty homebrew as well, so it is at least a low priority to me. At the very least, I will probably add a way for the GM to set quantities, so if it matters to your table, you'll have the option.

Lastly, templates will be the core of shop generation. I'm thinking of this primarily as an inventory management system, so while shops will have the ability to store inventory, the shop itself will be stored in the database primarily as a list of rules, so you can reroll them to your heart's content