Another good point about Calamondin is that it is reasonably fast to fruit from seed, maybe 5 years, certainly not 15.
The plant is on the smaller side, so possibly the node count for flowering is lower ?
It doesn't take too many growth seasons to get to full size
Either way you won't be waiting those long years for the hybrid to flower, depending on the other parent.
I remember reading about another Phillipines variety Calamandarin.
I think both it and Calamondin were also used as rootstocks over there.
Interesting that other Calamondin hybrids are not well known or heard of, even though Calamondin / Kalamansi is cemented in Philippines culture.
The success rate of hybrids is an interesting question.
If the rate is low, you have a few much wanted plants to deal with and a bigger bunch of unwanted plants to deal with.
You may be able to use these as rootstocks for the hybrids ?
I have found it nearly essential to graft from hybrids to ensure survival long term.
(Some of my most interesting unusual off type seedlings now only survive on rootstocks, the originals often died.)
Also you can easily then multiply a few hybrid seedlings to many seperate plants on rootstock.
Grafting to other more established rootstock will also push the hybrid to flowering faster by growth alone.
After that you can either repeat the hybridisation cross, or just grow the next generation seedlings of the first hybrid to get more variable " hybrid " types.
That might be more interesting if they are zygotic, as you are reshuffling the original hybrid cross for new versions.
If the hybrid success rate is high, you have a lot of plants to deal with, pot up, possibly graft, and assess long term for worthwhile characters.
I am pretty sure professional breeders throw out a lot of interesting stuff that doesn't meet the original reason for the hybridisation cross often based on arbitrary reasons.