It's on the list, Sally
Yep, we have two Shetlands, doing much as you plan - bull calves for beef, heifers for breeding. They are a dual purpose breed but most folk keep them as sucklers. They will produce calves to a Continental bull (although probably not wise to try this for a first calf from a heifer) but if you go for Shetlands, I would urge you to breed pure as the breed is SO endangered.
Ours are halter trained, so we just have a gate in the byre, hinged to the wall - we tie them up beside the gate and swing it over to pin their bums.
Shetlands are horned but of course can be dehorned, but I think they look better with - and if a cattle beast wants to hurt you, the horns issue isn't going to come into it.
The beef is absolutely tremendous, they are docile, small, live on fresh air, easy calving, no genetic issues (other than in bull choice if breeding, because of the small size of the gene pool, but there's good advice available). The breeder we bought our beef from this year had 168kg of beef from his 28 month old bullock.
We graze the sheep behind the cattle, rotating round five paddocks - this year we had zero worms in the faecal egg counts, so there must be something in this multi-species, rotational grazing management.
If you are interested in Shetlands, have a look on the Shetland Cattle Breeders Association website
www.shetlandcattle.org.uk - lots of good information and a list of cattle for sale.