I would consider the Flethcher "edit" 2200 or newer designs. They make it in a 48 and 60 inch size.
Great tool I have had a 2100 for years with no problems.
"edit"
I misread your post, as I saw mat cutter. You already mentioned you don't have a wall cutter. My question, can you mount a 48" wall cutter and how much gator are you using? Gator is much cheaper sold in the 4 x 8 sheet size. You will need to order through a framing distributor if possible or find a local source. I use a local plastic (sheet plastic) shop in my town, as they can order gator.
My main sizes on gator tend to be 16 x 20, 20 x 30, and 24 x 36 all on 3/16" any larger I go to 1/2 gator, different story totally.
A wall cutter is invaluable for making the first cuts, I trim down by hand using a long ruler and one of the self healing cutting boards sold in hobby store or art supply stores. Tape the ruler down on the far side to help avoid slippage which will happen during the cut. If the piece is going straight to a frame, with 3/16" you only need one cut and it doesn't have to be all the way through as you can snap the rest clean.
I don't use a mat cutter for the trimming and I don't feel a mat cutter by design would work well for the first cuts, although the 2200 Fletcher is designed to make such cuts.
A wall cutter can be found used very often, shops going out of business. Framingsupplies.com sells a very nice 48" for under 850.00. If you are doing a lot a gator it will save you a lot of time.
Paul