I’ve grown seedlings from Alba Semi-plena. Good plants, but most had badly shaped white blooms. They all took 3 years to bloom and many had none of the vigor of the parent. The Albas are mostly hexaploids and so you will likely run into fertility problems, and possibly deformities. I think there are very few hybrids around because of this.
I have used La Belle Sultane in breeding as well, with mixed results. It tends to pass on Blackspot resistance and hardiness, and often rich color as well. However, it also tends to create offspring with petals that curl badly, making for rather ugly blooms. As I say, mixed results.
Tuscany Superb has been a good breeder for me. It often passes on improved Blackspot resistance, but vigor isn’t always there. When crossed with modern roses, it doesn’t often pass on its wonderful coloring, tending more to deliver progeny in dark pinks. Offspring are often quite compact as well. Many seedlings are fertile and can be worked into another generation.
Queen Elizabeth is known for breeding seedlings with improved Winter hardiness. If you make some non-traditional crosses with it, you will likely discover that the old gal still has some tricks up her sleeve.
Crepuscule is extremely fertile and passes on some great things. Put its pollen on ANYTHING. Be aware that Winter hardiness is not one of its traits, however.
Although people have had some success using Mutabilis in breeding (note that most known offspring are open pollinated seedlings) I had very poor results with it. Its pollen is rarely accepted on other roses. Again, Winter hardiness is not something it is likely to pass on to progeny.
As already mentioned, William Lobb is something you should consider. It is highly fertile in both directions and has produced some very beautiful seedlings for me. I have a new seedling soon to be introduced that used Lobb as the pollen parent. Passes on good vigor, good disease resistance and often, excellent color. A useful parent, IMO.
Good luck, Max!
Paul