Let’s assume your claimthat exercise being good for mental health is true, and that it is Imperial’s duty to deal with this problem.
Ok. So Imperial needs to get more people to exercise. Anyone who has been to the gym at Ethos knows that at least 50% of the treadmills are being walked on, and at least one of the rowing machines is being used by someone moving the seat up and down under him/herself while somehow keeping the handle in exactly the same place, putting precisely 0.2 calories per hour of power through the fan. The point is, there is absolutely no need to increase the size of the gym. People are perfectly capable of walking all of 100m to Hyde Park for a jog, or even joining the cross country club if they feel unable to run unsupervised. Indeed, I would particularly recommend that last one. The club is the largest sports team at Imperial and has a great social scene.
We have to, of course, spare a thought for the minority who actually use the gym in a mildly wise manner. Perhaps there should be a treadmill walking ban, or even the removal of half the treadmills to make way for actually useful gym equipment. Additionally, students might be interested to know that Reynolds gym is also available to students to use, although they may have to interact with the outside world on the way there.
If you really want to spend some of the money Imperial has, may I suggest investing it in some more scholarships for extremely talented students. After all, this is a university.