1) The technique you're describing is going to lead to very long journeys, so this makes manned flights impractical. Or am I wrong? 2) Getting something to a L

1) The technique you're describing is going to lead to very long journeys, so this makes manned flights impractical. Or am I wrong? 2) Getting something to a Lagrange point is only useful if it's at near zero velocity (relative to the point) when it gets there -- otherwise it falls off. So, either it gets there slowly or it burns fuel to stop at the right spot.