I can't suggest any solutions for the remodel. I suspect there will be solutions though for the mine.
- trash the best treasure in hand (according to its trash priority) and get the most desired treasure from the supply according to player’s buy rules
This results in ventures and royal seals getting trashed for gold when copper or silver is in hand. I can see a variety of situations occurring though where treasure cards outside the basic supply should be mined first, so maybe some decision making is needed. Looking through the treasure cards I'd suggest a mining priority in roughly this order:
Gold
Contraband - Situational but removing contraband before the end game is usually desirable.
Loan - Situational. Always mine ahead of silver/copper seems reasonable.
Talisman - Situational. Always mine ahead of silver/copper seems reasonable.
Quarry - Situational. Always mine ahead of silver/copper seems reasonable.
Silver
Copper
Hoards - Situational. Only mine after basic treasures seems reasonable but mining up to platinum could be better.
Royal Seal - Situational. Only mine after basic treasures seems reasonable.
Stash - Situational. Only mine after basic treasures seems reasonable.
Banks - Situational. Only mine after basic treasures seems reasonable.
Harems - Situational. Only mine after basic treasures seems reasonable.
Horn of Plenty - Situational. Only mine after basic treasures seems reasonable.
Ventures - Only mine when no basic treasures are present.
Potion - Mines and potions can be played cleverly by humans but probably best to never trash potions with the simulator.
Philosopher's stone - never intentionally mine this.
Diadem - Never intentionally mine this.