Was there no alternative? Did the Ripple network have to use a cryptocurrency of its own? Why not simply use Bitcoin for paying of fees? Integrating Bitcoin into Ripple, eh? Paying fees with Bitcoin, that is.
Also couldn't a Ripple System be made that doesn't use a blockchain?
Not a decentralized one.
I guess that it could have been solved in other ways too, but I'm not sure how that would work in a decentralized way. If you have ideas, feel free to post them.
Because Bitcoin is horribly slow compared to Ripple, 0-conf transactions are not safe and Bitcoin is built to be probabilistically stable, not absolutely (meaning it is very hard but not impossible to reverse a transaction that made it into a block). There's also the issue that in Bitcoin only individual miners choose what goes into a block, not the collective network.
This would also mean that besides running Ripple, one needs a full Bitcoin node to make sure that transactions are being paid for.
The first Ripple system by Ryan Fugger on villages.cc used a central server afaik.