2 things.
Trimming the mats really isn’t that bad. You just need sharper knives maybe? I worked at a barn that completely gutted and re-did all the stalls while I worked there–new walls, floors, etc. The floors were packed limestone with rubber mats cut to fit on top. Contractors installed everything, because they were also installing the new walls, but they did the mats an entire 24 stall barn in 2 or 3 days, and there were only 3 or 4 guys working. I can’t remember exactly what they used to cut them, I know they went through a lot of blades, but the hardest part was getting those last pieces in, because the fit had to be snug. I think it was like really heavy duty exacto-knives. I know it wasn’t a fun job, because I helped a bit, but it wasn’t so prohibitive that I would look for alternatives, because I think that is the best option.
Second thing–people saying “bed more” are unrealistic. Bedding is damn expensive, one of the biggest expenses a boarding barn has. My barn has 12 X 12 stalls, concrete floors with rubber mats, and I would say we put about 3 inches of bedding down (the wood pellet kind). There is absolutely nothing wrong with that amount of bedding. I know people like horses swimming in fluffy shavings, but that is not only a PITA to muck and a waste of shavings, but cost prohibitive unless you are charging like a grand a month for board. I consider myself to be a bedding Nazi–I like a horse with a soft bed. If you had bare concrete or limestone then yes, you are going to have to bed more, but in the long run it is so much cheaper to install the mats and bed less deeply. I know some high-end barns where the horses get a skiff of bedding over their pee spot and that’s it. I don’t like it, but horses don’t “need” 10-12 inches of bedding either. People that think that are usually boarders who have never kept a barn in their lives, or people who keep horses at home and only have a couple, so the costs and difficulty of it don’t really dawn on them.