Just an FYI, during the next protocol upgrade there will be a warning displayed in the client when > 20% of the last 2000 blocks has a protocol vote higher than the users current protocol version. This was added in 4.0.
It won’t display this time unfortunately because 3.0.2 clients don’t have the warning code. After this protocol upgrade though the client will automatically notify when the threshold I mentioned above is reached.
No need for developer messaging. Shareholders will inform the network automatically simply by using the protocol voting when they mint.