The theoretical issue of reduced security caused by fewer nodes staking can be addressed through explicit balance leasing from lightweight nodes to full nodes. By leasing their balance to a trusted full node a lightweight node actually increases its chance of collecting transaction fees, since it does not have to stay online, and the full node has an increased chance of producing a block due to its increased balance.
I'm posting this again since I think this was in the whitepaper
I feel like another ICO had a similar idea but I forget the name if anybody can help me.