Here was my criteria back in my days working plainclothes:
1. Jackets should be about one size larger than you usually wear. This may require some alterations such as shoulder seams, shortening sleeves, etc. Full cut is better than a tailored cut. Single center vent is best, assuming strong-side holster placement.
2. Have a band of light canvas about 10" wide sewn into the jacket linings around the torso area. This will do a lot to prevent "printing" while also protecting the linings from sharp edges of the gun, and also allows for an easier draw.
3. At the bottom corners of the jacket have a couple of heavy fender washers stitched into the linings. This allows you to sweep the jacket out of the way and helps it stay open during the draw, while also making the jacket hang straight and neat so as not to expose your hardware.
4. Suit trousers will seldom allow for a sturdy gunbelt, loops are just too narrow. Have them save the material cut off when cuffing the trousers and use it to make larger belt loops and have those stitched on at locations that will not interfere with holster placement, mag pouch, etc.
This can get a bit expensive, since you are having the suit altered considerably. The good news is that since your suits have been extensively altered solely for business use the entire cost can be tax-deductible. Save all your receipts.