You could probably earn a quick $150,000 or so in BTC donations, just for
fixing ReaperMine.
Best to pick the low hanging fruit first. Then work up to greater understanding of the Bitcoin and altcoin ecosystem, so you won't waste effort on overly ambitious wide-eyed challenges that will have a higher probability of failure.
If you are experienced developers and entrepreneurs, then you understand the value of incremental development, release and learn through the immersion in the market.