I really hope you will release your code (and give regular updates) as soon as possible, I'm unsure why you want to introduce PoW for the transaction level though (sounds like Bitmessage) if you still want to keep a native asset (XSP) around.
As far as I understand, XSP will be mined (e.g. you set a certain number to be mined per 2 weeks or so and adjust difficulty, just like Bitcoin and then instead of using PoW to verify all transactions you just attach PoW to individual "coinbase" transactions). Why not modify the existing Ripple implementation to have XSP as additional second native asset next to XRP? BTC also are a good (by far not the best, but at least an okay one) candidate for additional native assets on Ripple.
Anyways, again, please share code as early as possible and good luck with your endeavours!
As far as I understand, XSP will be mined (e.g. you set a certain number to be mined per 2 weeks or so and adjust difficulty, just like Bitcoin and then instead of using PoW to verify all transactions you just attach PoW to individual "coinbase" transactions). Why not modify the existing Ripple implementation to have XSP as additional second native asset next to XRP? BTC also are a good (by far not the best, but at least an okay one) candidate for additional native assets on Ripple.
Anyways, again, please share code as early as possible and good luck with your endeavours!