PM sent.
My ideal Dominion randomizer app would do the following:
Allow me to enable/ban any particular expansion or promo, or any particular card.
Allow me to specify a minimum or maximum number of cards to be used from any of the following sets:
any expansion
attacks
reactions
villages
trashers
draw cards
treasures
Alt VP cards
cards of a particular cost
(I'm sure I'm missing categories here, but you get the idea; each card will belong to any set of these categories, you know)
^^ most Dominion apps out there will do all of these things already, particularly Dominion Shuffle which is the one I use right now. The features that you can't find out there that I think would be useful are:
allow me to select any number of kingdom cards! All of the apps make me pick exactly ten cards (if you could Young Witch+Bane as one card, which you should), but I don't always want to do that! What if I want to play in veto mode, I'll want the app to give me 12 cards (or 13 or more if there are more players). What if I want to playtest a fan card (or a few fan cards)? I'll want the app to give me only 9 cards (or less if I want to playtest a few).
The display: Hermit and Madman should be on the same line, not appear as two separate kingdom cards. Same with Urchin/Mercenary (in fact if it was me, I'd just store those at the names of the cards and be done with it).
If there are Shelters, Colonies, Ruins, Spoils, Potion, etc. put a nice little reminder of that somewhere like the other apps do, but don't mix them with the kingdom cards. I don't know of anyone that stores their Potions with the P cards.