I like roman shades, but I'm not a fan of having that extra fabric at the bottom. Here's a photo-- (not sure if this blind is just half lowered? I can't tell) But imagine those extra folds at the sill. Maybe it's OK? It's your call. You could always buy one, hold it up (or even mount it) and see if you like in your home and take it back if it doesn't work.

My guess is that it will cost a bit of $$$ to get them shortened, since you have the fabric, lining and the hardware. Maybe you could call a local seamstress to get a rough estimate. There are a lot of companies who make roman blinds, maybe shop around or consider custom shades. FWIW, I made some myself ages ago and I'm not particularly handy. So this project is definitely do-able, if you have basic sewing skills and patience for DIY projects. You can google utube videos.

They can be shortened, but will not be cheap. They also should be vacuumed only.
When I make romans, I leave enough for one extra fold. Any more can look too bunchy.

My problem is with the width. I know you think 26" will be okay, but it's not. They'll be too narrow, leaving too much space at the sides. Not only does it not look nice, but if you're wanting blackout, you'll have too much light coming in.