Originally Posted by mteran
i guess my main question is. if one were to take in the armpits should i look for
suits that are 2-3 sizes bigger for the extra fabric needed? should i look for bigger
sizes in the 4-5+ range, etc?
An armscye is a hole. How are you going to fill it? It is an empty space. Were you hoping excess cloth could be turned into a patch?
Admittedly, you can make the armscye smaller by opening up the sideseam and underarm seam where they join into the armscye. You take a section out of the armscye at these points. You will have to remove the sleeves, unpick them, and then fully recut them and reset the sleeves so they fit into the newly narrowed armscye. You will have to ensure that the sleeve pitch is correct when the recut sleeve is sew back in. The lining will also have to be recut. The side pockets will also have to be opened up and then remade. You will likely require one or two fittings as on a bespoke coat.
All in all, you are looking at about $1000+ of work. It takes twice as long to do this as it does when you are making a coat from scratch because you have to first laboriously unpick all the seams, then recut and then stitch it back up again. This requires highly advance - bespoke level - tailoring skills. Any sensible tailor would refuse to do the job, and anyone competent enough to do it well should charge a minimum of $2-3000 for it.
In the end, as Bengal says, it will still go to charity because the pockets and button positions will be too low. You can also only narrow a coat so much because the pockets start to get in the way.
I suggest that if you are going to do it, do it yourself. Buy a good book on how alter coats and either get a sewing machine or learn to hand stitch. At least this way you will learn something useful. The project will take about a year or so, unless you are an excellent sewer already, when you could learn in about 3-6 months of intensive learning.