After a night of rest, I found out that the theme was not exactly an easy one. At least not for my self-established goal of coming with mechanics related to it. After a couple I couldn't think of anything really interesting beyond the obvious (using your life or hit points to purchase things).

So let me try to at least be a bit creative with the interpretation of the theme: you, the player, have worked all your life on the mint (your life is currency!). Your work is to keep the mint producing coins, despite all the challenges that happen in the everyday minter life (I don't know... visitors, thieves, ghosts...). You need to maintain the coin production at a certain rate (because, yes, your life is currency also in the hit points sense).

You can also buy stuff to help you keep the mint working, but this costs currency/life, so you need to judge if buying stuff helps more than it costs.

Sounds like a plan (if not a brilliant one). Let's see how it works out!