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Instead of always allowing you to draw 3 cards all of the time, (which could be overpowered from time to time) how about modifying the Draw & Buy Cards rule to give you a minimum hand size of 4 cards? So if you end your turn w/2 or 3 cards in hand you would still draw 2, but if you played all of your cards you'd draw 4.
This would prevent those turns where you've only got 2 or 3 cards in hand, which is what the real problem is (a lack of options) while still keeping the game's original design of never having more than 5 cards at the start of your turn.
Why would I ever not exhaust my entire hand if I knew I could replenish to 4 cards every turn?