So to your general question whether you need to decide right now whether you want to fly to Japan on JAL or ANA, you don't. If you're willing to apply for business credit cards with your nascent eBay business, you can start working on cards that can earn you points currencies good towards either JAL or ANA and still maintain your under 5/24 status to stretch out the number of cards you can get from Chase and other issuers.
I hope this helps! I'm sure there will be more replies coming to help! Take a moment to digest it all and follow up with any questions or details that might help us help you more.
When you're ready to apply, we can help walk you through it if you still need it. If and when you do apply for any new cards, and you don't have a "support" link for that particular card, it would really help give back to the community if you first check the DISchurners support links pages to see if you can find an application link for the card you want. It only takes a few seconds, but when you apply through a fellow DISchurner's link, you show that their help, advice, shared experiences, and contributions are appreciated.
Good luck!