@JohanPlukon Been scratching my head about this one recently as well 😉
I have a setup with 2 server rooms which are meant to be redundant (so 2 internet lines, 2 servers connected in HA and so on) with 4xMS425 stacked together (2 in each server room).
I was thinking about splitting them so I would have one stack per server room - avoiding issues that come with Meraki stacks with 3 or more members and also staging the core stack upgrade (which handles our L3 and internet) therefore avoiding downtime.
But as you said, there is a lot of things to consider.