I agree with bloke. If it's too "stuffy," then just have a larger leadpipe made.
I have a friend coming back to brass after being away a couple of decades. He used to be a trumpet & french horn player Yeah, he did both. How, I'll never know, as when I was still a trumpet player I tried a french horn for a year in undergrad, then ran yelling and screaming to the trenches, where I remain today!.
As a comeback horn, he purchased one. He uses a Schilke 50 mouthpiece with it. The combination for him is just right: good tone, good range, good breath support. He tried a couple of the more conventional comp euphs with the usual larger bore and leadpipe, and they took more air than he could provide. As he gets back into it, he may get enough breath volume and support back to go to a bigger horn. But if not, all he's ever contemplating is community band section work, and for that it's fine.
Those who say it's stuffy should remember the horn was designed for beginner to intermediate usage, not as a college or pro horn. So a judicious amount of resistance is engineered in for a moderate player to help with the breath support.
The really nice attribute to the horn, unlike a lot of current really large bore euphs, is that instead of a huge dark sound that is becoming the choice for especially soloists, it still has that (in a technical definition) horny quality that will help it project as a section in a good band without sounding pinched or overly broad as to not blend, either. That attribute would probably not be affected by the change in mouthpipe, which being detachable, should be comparatively inexpensive to fabricate.
Being a non-comp, it's also a lot less expensive, even with the extra mouthpipe, than a comp. And face it, unless you live in the basement on a euph, the only two notes that are actually different until you get below the staff Eb is 2nd line B nat and below the staff E nat, which are both a little sharp fingered 2-4 without the comp loop. Everything else from there up has theoretically the same primary fingering and the same general characteristics.