Apologies for not reading the whole (redundant) thread, but at the risk of being redundant myself, there is nothing that can be played on four string bass that can't be played on a six string bass. The reverse is not true. If you can wrap your mind, as well as you hand around it and are willing to put in the time to master it, rather than whining about how hard or nontraditional it is, it may be perfect for you. The only people that are going to snivel about you playing a six string bass, are other bass players who can't play one.