Should we encourage people to stake Mina outside exchanges and how ?

In my opinion, any project that cares about decentralization should promote non-custodian HODLing/staking.

MF delegation enforces hi-uptime and good behaviors on the validators’ side. And, there is also a rule that limits concentration.

Why not encourage holders to delegate to them…

Also, Polkdot enforces decentralization at the protocol level. I think that PoS blockchains need such a mechanism. There are proposals about it here: Long Term Decentralisation ideas? - #19 by TauLepton