Is it possible to build Wilkinson power splitter using (3/4)*lambda lines?

Idea is to replace lambda/4 lines with 3*(lambda/4) line. Or 90deg with 270deg. In this case path between two ports will be 270x2=540deg (out of phase180 deg). And quaterwave transforming still works: d=lambda/4+ m*lambda/2... Is it correct?

Yes, correct.

sure, but it will only have 1/3 the normal bandwidth