Moving the mainsheet to the end of the boom will give you better mechanical advantage, so it will be easier to sheet in with the same power tackle.
It also, obviously, makes a larger dodger possible.
The bad (maybe)
If this puts your traveller mid cockpit - then you'll have a shin banger you didn't have before.
If it puts your traveller at the aft end of the cockpit, then unless you run the mainsheet forward somehow, using the mainsheet from your normal steering position will be more awkward (you need to reach behind you with your "off" hand).
IMO moving the mainsheet aft on the boom is better than going the other way.
btw - not really sure what you mean by your traveller being "directly over the companionway".