The problem with using soft outsoles on tennis shoes is that they'll wear out in no time especially if you play on hard courts. That's why most tennis shoes have tough and harder outsoles so that they'll last longer, especially the ones with the 6-month outsole warranties (or else the companies will be sending everyone free shoes).
You may want to try a clay court shoe as those are more likely to be made with a softer outsole since playing on clay doesn't wear out the outsoles nearly as quickly. Try taking a look at these, but I would avoid the ones with the outsole warranties since they have to make those soles harder to be able to offer the warranty.
http://www.tennis-warehouse.com/catthumbs.html?CREF=138