I had the exact same issue with my '05 Sirrus Comp. I was changing the stock crank (compact double 50/34) to a 50/40/24 road triple. What I didn't realize, is that you are supposed to get a wider BB in this case, otherwise the middle ring will sit where the inner ring of the double used to be. Or something like that.
The thing is, I was perfectly happy with the chainline with the existing BB. Yes, it was displaced by 1/2 to 1 cog inward from the center of my 9-speed cassette, but I could argue that this was *better* for my gear usage, and at worst inconsequential. The problem was that stupid FD
compounded by the fact that I needed a special one designed for flat-bar hybrids.
I ended up going the dremel route, but it was a lot more involved than just cutting away a bit here and there. I actually moved the two pivot points, and in the process used some JB weld, did some soldering, and learned to wind my own carbon-steel springs! The result is not pretty and may well fail after a season or two. When that happens I will probably have to do the "right" thing and change the BB. For the time being, it works great!
What is frustrating is that the Shimano FD designs are "lazy" in that they could easily provide more inward travel, but they don't. And because nobody specs this, without a box-full of FDs to try, it's nearly impossible to select one based on that criterion. All you will find from google or BF are answers to the effect of "well, duh, you need a different BB," but that really shouldn't be necessary.