Very interesting and very ambitious project you are attempting here.
I see real potential here. Blockchain is perfect for decentralized ownership of virtual assets. However, to pull it off is going to be quite a project.
Here are some ideas to consider as you move forward.
Keep the blockchain aspect as simple as possible at the start. Bitcoin only does one thing allow bitcoins to move from one address to another but it is still very complex at the code level. Keeping the initial features simple at the beginning will lower costs and the number of programmers you will need. You can always add more advanced features as time progresses with hardforks which are going to be needed when you release new expansions anyways.
Mining is expensive and dominated by big players. Assume that 80% of the mining will be taken over by people with massive GPU farms who will then dump the rewards on the secondary market. Players are not going to be the primary miners.
Rewards to miners only need to be high enough to secure the network. If miners most of whome will never play the game get 100% of new cards you might be starved for revenue and lack the resources to attract onboard new players.
You may want to consider a gradually increasing reward schedule giving your company a large amount of the initial cards. Something like the miners get 25% of the initial cards the first year with that amount increasing gradually over time. This would give you a product to sell to game stores and individuals. Rewards to miners just need to be high enough to decentralize and protect the network.
- Rarity at the code level. The reserve list in magic is something to emulate perhaps at the code level. Some kind of code limit that only allowed 95-99% of each set to be "reprinted" in future releases would help build speculative interest.