This was exactly my issue. Making the chest fit would mess up the shoulders. For pants, making the thighs fit meant a huge waistyou have a very prominent chest and it may be hard for you to get a good fit in RTW. Just going up in the chest size may lead to shoulders being too wide and too much room in the back. The trousers will certainly be too large for your drop.
you might actually be the uncommon person who needs custom, but the person fitting you needs to recognize your fit issues and the system they use has to be able to accommodate the necessary changes to the block pattern (if you’re using MTM).