I used to sell alot of sheep direct to the public and still have a couple of ryelands because my little boy likes them....
I also butchered my own usually;
Ryelands do have a tendency to be alittle fatty in their second year and also their body is not really easy to cut.... It dissent lend itself to easy neat cutting to produce consistent chops like a commercial breed does, and their can be alot of trimming required. The main isssue is their body shape, a sort of R to O grade carcase and a tendancy to cover everything in an even layer of fat, and the joint and chop shape is a little all over the place from sheep to sheep.
If the person butchering it normally does mainstream breeds (which are just that for a reason!) then they may find the ryeland a pig to do - I honestly didnt enjoy cutting them, as they took alot more time to make a good job of, and required alot of trimming to make the cuts presentable.
That said the meat is fine and pretty much equal to any well cared for commercial sheep, and they do carry to heavier D/W before they go fat (I found 25-28kg carcase weight was possible before they became tubsters).
Perhaps cross your ryelands with a suffolk to get slaughter lambs which are easier to produce a consistent product from. You then dont need to keep any lambs to breed from but have a very saleable sheep - a suffolk cross will sell well in the market and with the ryelands plumpness they do look very good at 42-45kg live weight and sell strongly (£70-800 not unreasonable).
It cuts both ways - primitive breeds are a bugger to cut because they have a different shape all together at the other end of the spectrum, hardly any fat and long lean frames!