I say he would be better in the OF because hes always had issues with footwork. Yes, he has improved and is still only 20yrs old, but playing 1b requires a TON or proper footwork to play the position adequately. 3rd base requires a good quick twitch reflex. If hes getting slower with footwork and reactions, not sure a corner IF spot is the place for him.
I think LF would be a solid fit if SS doesnt work out. Just has to learn the monstah and belt 30+hr and 100+ rbi...Your typical slugging corner OF'er. With his good arm he would compile a lot of OF assists as well.
Ive seen him play in person a few times and he does look a little awkward out there. Hes good, but hes not an incredibly agile big man. If he fills out a lot this year and it hurts his development at SS he will be moved. If I was a betting man I would say LF.
While footwork and quickness are both needed at 1B and 3B, my quess is that most SSs have the quickness that can translate well to those corner positions. If Boggy is not "quick enough" to play 3B or 1B, then he'll never make a very good fielding SS and should be moved somewhere soon.