Regarding the stairs comment above, I once had a client suffer a "once in a lifetime" flood, I didn't have to look after their location but one staff member had the fun task of emptying a 42u server cabinet on the ground floor to the upstairs offices as the water rose up. Needless to say in some facilities in the UK, the server room is never on the ground floor.

I'm not sure where you are based, but one thing I consider in the UK is power.
I often see circuits in old offices and everything from server cab/room, office PCs, aircon units, electric heaters, kettles and all sorts of random electricals end up on the same ones and when X device trips a rcd or circuit breaker it causes a lot of IT issues it didn't need to.

I try to get sockets that will serve user computers on their own dedicated rings separate from all other plugs also separating rings for the server room and putting in RCBOs for each which act as circuit breaker and rcd in one unit (relatively new in UK) rather than a single RCD for many circuits.

Following on from above, what if in the future, management say they want continued operation of critical business equipment in a power outage (Happened to me just before Christmas when storm damage cut off some offices and they were looking at a couple of days without being able to function).
That is going to mean a large UPS and generator setup (or a lot of batteries!). Where will the generator end up physically located (thinking of noise, exhaust, etc) but still be in an ideal location to reach the server room and electrical boards. I have that quandary at this site.

Connectivity services - can you get ducting installed to 2 sides of the facility and have connections enter the site from 2 directions just to mitigate someone down the road accidentally excavating a cable/ taking out a pole you rely on.