It's very interesting. I must admit, i don't know much about citrus breeding, the only thing i have understood is that citrus usually show some characteristics in the offspring wich are intermediate among the parents.
Given this, i was thinking, maybe if siamese sweet worked so nicely as parent tree, it would be interesting to attempt to cross it with one (or more) of the palatable hardy papeda (i was thinking to shangyuan lemons) in order to attempt to get some nice offspring from such cross, with valuable characteristics, what do you think?
Few years ago i also managed to get a corsican citron, which should be acidless, with the same idea in mind, to attempt to cross it with some other citrus (nagami kumquat was my original idea) in order to attempt to breed an interesting citrus.
I see that also maltese orage are acidless, but they are also not much interesting for breeding.