I know a couple of people who did this whilst they were temporarily working overseas. However, they remained employed in HK and were seconded to the overseas office (Singapore and Dubai in these cases). They received their salary and were taxed in HK as least partly, and they retained an address in HK (possibly only a flat share though). They came back to HK a number of times per year, although they were away for the bulk of their time for those couple of years. They then returned to a full time role in HK, and I think had a couple of years full time residency here again before they applied. I don't know what supporting evidence they gave, but probably a letter from their employer that their time overseas was essential to their role in HK.

I think there is specific guidance somewhere that the time young people going to boarding school and uni counts towards the 7 years. But in those cases they probably have parents and a home here. You'd probably need to convince Immigration that your case is the same - maintain a home and return to it for every holiday.