Of course it's possible. Such an alternate PT would basically be a trilogy of fan films, and SW fan films already exist in great abundance, so it isn't outside the realm of possibility.

The biggest problem facing such an endeavour is getting everyone to agree on what the storyline should be; everyone has their own ideas on what the perfect PT should be, and not everyone is going to agree, so compromises would have to be made.

There is also the issue of commitment that has to be dealt with. You can't get anything done if you're only half-heartedly interested in doing it.