Yea the blockchain size is a very real issue, it's one of the reasons I don't use Bitcoin Core. I'm fairly sure this problem is relatively high on the priority list and that the devs will have a solution ready before the size reaches 100's of GB. Personally I can't really think of any suitable method to reduce the size other than maybe implementing some state of the art compression mechanism (good thing I'm not a core dev
) Else we forgo decentralization and have big companies/entities shoulder the cost of hosting the blockchain on their servers