Trade Between Altruists With Different AI Timelines?

Suppose Alice thinks AGI will probably happen in the next 5 years, that this will lead to an existential catastrophe, and that spending on AIS has by far the highest value right now. 

On the other hand, Bob thinks AGI is far away and donations to AI Safety aren't very impactful. Bob thinks that donating to global health charities is by far the best use of money, and that this will stay true for the next decades.

It seems Alice and Bob could benefit from a trade. Bob donates to AI Safety until, say, 2030. If no existential catastrophe has occurred by then, Alice donates to Global Health until she donated a sum of money higher than what Bob had donated to AI Safety (plus interest).

This way, both get more money into their cause area at a time it matters to them.

I am keeping this short, feel free to ask for elaborations. I know there is some literature on moral trade and betting on beliefs. Is there anything on this in particular? Is there maybe even some kind of initiative to facilitate these kinds of trades?