I wonder if there would be more success by marketing to companies instead of individuals?
Certainly some companies spend more than $10k on specific people. Lets say AA approaches Company xyz and says your Employee 123 spent $15k last year but never made it beyond PLT, here's an offer to prepay $10k and give them good benefits to start. Employee wins and AA wins. I'm not so sure about company winning and with Sarbanes-Oxley, this card would be another thing to keep track of when the funds are actually used versus held as an asset.
I just don't see who the target audience is for this. I'm thinking companies but how many are going to want to park funds into AA. Travel arrangements are often on the lowest price, not investing in certain airlines. If enough people buy these cards (or gift cards for that matter) AA could slightly increase prices knowing that a certain percentage of people are going to fly AA just to use the cards they have value on.