5mm diff in chainline. Hmmm. Have you tried backing out the high limit screw on the FD all the way? Yes, a shorter BB spindle will help, but 10mm sounds like a lot. We had a Shimano 105 equipped Raleigh Coupe and I changed the 30T granny to a 24T and the FD handled the difference just fine. I changed the 42T middle ring to a 39T which actually makes more of a difference to a FD, and there is also not much of an issue. Before I spend money changing any more variables I would be looking at those limit screws. A new FD might work and you only need one. And you could make sure it is optimized for a compact crank gear range but you will spend who knows what. Last would be new BB's because you would probably want two (you don't 'need' two but its what I would do). The new unit BB's are common as salt and just as cheap, but you can spend more, much more, sky's the limit with those things. Something in the $25 ish range each should do you fine but I'm not sure you need to go 10mm shorter. 5 should do it.