Soay cross breeding idea

Starting to think ahead a little.  I have 7 Soay sheep at the moment, a ram plus 4 ewes and 2 lambs.  Intending to keep the ewe lamb in hopes of additional lambs in the future.  Ramling is possibly going to be sold as I don't want to butcher him this fall (nothing against butchering, I've done it before and will probably buy a butcher quality sheep or goat with the proceeds from the sale), but also don't want to mess with keeping him separate from the ram during rut.  Especially since I don't have a wether to keep with him, and buying one just for that isn't feasible right now.  

Anyway, the ram is 3 years old, so rush to replace him.  He's probably got 8+ years of good service left.  But, at the same time, crossing the ewes with a larger breed might be nice in order to get larger lambs for butchering and to take advantage of hybrid vigor.  One idea I have is to get that larger breed ram and put the ewes that produced from the Soay ram with that other one during rut, and leave the unrelated Soay ewes with the Soay ram.  Eventually I'd need a different Soay ram if I wanted to maintain that herd long term but it would be easy-ish to just shift around the ewes depending on how I wanted to get replacement ewes.

Soay have a wider pelvis relative to overall body size than most other sheep, and combined with the lambs being smaller at birth means usually super easy lambing.  Which I like, a lot.  Soay lambs also grow super fast and usually proportionally more than enough to catch up to other breeds, they just stop at a smaller overall stature.  So I think I want to maintain a pure Soay ewe flock for now.  Any non-Soay ram I might get I'd treat as a terminal sire and either butcher myself or sell to others that want to butcher them.

What would be some good non-Soay breeds to consider for this project?  Obviously I want them to be larger, but not tooooo much larger as I don't want to cause lambing difficulty.  Lower maintenance is highly desirable.  So something with at least decent parasite resistance, and if there's a hair (so naturally shedding) breed that would meet the other requirements that would be great.

I'm not a sheep expert, but live in a sheep area.
I believe locally they sometimes use Texel for terminal rams - most ewes are cheviot or blackface.
I don't know whether this suggestion helps.

Have you considered Shetland? They're slightly bigger than Soay, similarly short-tailed so they don't require docking, and are generally considered low-maintenance. Some but not all will naturally shed their wool, so you'd just need to find a breeder who selects for that. (They also tend to have a finer wool, but that wasn't one of your considerations.)