What would the angular and acceleration tolerance of such a burn be? Seems to me that one burn to hit a target point (range half million miles) whilst doing a >180 degree gravity assisted swing/about turn would need very impressing GNC. If you will require correction burns then you'll have to burn again anyway, which means that we're back to at least two burns. If you're resigned to that and you're taking all the trouble to get there, then you might as well go for three burns and do lunar orbit - restrictions being fuel and life support. The degree of comfort (mass) that you elect to lug about with you of course impact on mission delta v, fuel and life support timescale.