If you're having a custom shop do the fronts, that would be a question to pose to them. They may want to see the drawer boxes on site to determine the potential.

You can definitely change the drawer front sizes to anything you want. If you keep the drilling lay out (Which you would for the bottom drawer anyway) you can adjust the upper drawer drilling if need be. If you stick to 32mm increments you probably won't have to. We make custom fronts for Ikea and change the size to fit the look we are going for. Here's a example on one kitchen.

Thanks for confiming Jdesign. I'll adjust the drill holes on the drawer fronts.

Not sure you have to adjust the holes. Just said you have that option if needed. You have to lay it out and test. I would get a few of the really inexpensive Haggeby fronts taller than you need and cut them to the size you want for a test mock up before I did anything. The bottom drawer will not change but you screw the front connector in different hole locations on any Ikea drawer.