Regarding the introduction of new ssp I would consider two things:
- Choose ssp which are not sensitive, like many ultra-tropicals, which are very finicky regarding water, ph, soil, temp fluctuations, etc. Since apparently there is nobody over there who has the same dedication for the plants as you, better choose plants that do not need that much care
- ssp which do not fruit at the same as mango will get more attention by locals. For example black zapote, green zapote, ross, abiu, caimito, artocarpus, atemoya, a. reticulata, casimiroa tetrameria, etc... sapodilla and mamey fruit at the same time but are a must
Regarding the grafting skills, its all about practice