Being involved in the amateur breeding 'craze' has given me new respect for just how challenging it is to find an F1 with the beneficial 'heterosis' of some kind that would make it worth the effort to produce F1 seed for use or sale.
Commercially there's always a strong focus on the disease resistance traits which can only be 'stacked' in the heterozygous condition.
Heterosis for higher yield is another desirable, but parent plants with that 'combining ability' may not be that common.. perhaps some more experienced breeder could give a statistic on the frequency of finding such beneficial effects in the F1. There are specific traits to look for in one of the parents to accomplish that goal, afaik from what's been published (although there are also likely multiple roads to the same goal).
Yield heterosis would be a great target, if the heirloom parent(s) you have in mind are delicious but scanty producers. Finding an F1 that boosts production and yet really similar fruit to those scant producers would be really worthwhile.
I was disappointed last year growing out 9 F1 crosses and only found any earliness heterosis in one of them. The others were consistent in earliness of flowering matching the later parent.
On the other hand, some of the F1's that were reasonably early productive and tasty were not as much fun in the F2, making me think about those F1 seeds as perhaps more worth growing than other generations in those lines.
Anyway, you might try 'combining ability F1' or similar search terms to find helpful research that's been done... good luck and please keep us posted so we can learn from your project, if you will!
