I've tried the Invaders in a LP, and despite what most people say, it sounded great! Not 100% certain what it would sound like in your axe, but I'd say go fer it
If you put an invader in there I can assure you there will be a big difference!! It should work good though in an SG unless the guitar is already fairly dark sounding which most SG's aren't. Also, don't be totally afraid to go Invader in the neck as it is much lower output and doesn't have as much low end as the bridge. (Check the specs).
OTOH, the other neck pickups mentioned will also work well. You may notice a fair amount of output difference with them compared to the Invader bridge though. You might also consider a JB bridge in the neck spot.