That's an idea I was thinking a lot about. Generally speaking this is a good idea, with the expected limitations.
You have to follow the rules of the original game: lets say you want to use monsters from splinterlands. Now you have to be aware of the card blending mechanics and build your game so this won't cause errors.
Bound value: what does the card worth now, and what will happen to the price if your new game introduces some unwanted loops?
If you want to use existing tokens or NFTs there is no conversion, there is simultanious use.
- one game? simple
- two game? more rules to follow
- N game? exponential complexity