The instant question this title raises: how hard would it be to move a planet into close orbit of the sun?

Weirdly enough I never came up to a similar scenario in countless sci-fi books. I'd imagine it would be so expensive that if we were capable of it we would probably wouldn't need/want it as other alternatives would be much more efficient, right?

The thought of designed solar system is interesting - what if we FTL is an unbeatable barrier - we might just be stuck here and populate our system with hundreds of rogue passerby planets!