It's been a long time since I've been in as a reservist, but making a very wild-***, non-professional guess based on the tooth-to-tail ratio that seems to exist now, I would daresay we wouldn't be able to deploy more than a company-sized formation for anything resembling combat operations. Two companies might be a stretch, or somewhat feasible, depending on operational taskings and tempo.
Even then, such numbers are too few to permit full-scale combat operations. A force that size could probably handle force protection, with limited numbers hived off to conduct site recces and route-proving patrols if the main body needs to move to a different location.
One problem is that the proposed deployment is intended to conduct some sort of peacekeeping operation in Africa. That is, in an environment where a Rwanda-type situation could erupt with little to no warning, and where trying to conduct combat operations while vastly outnumbered by either side of the conflict could result in large numbers of casualties and inability to meet your objectives.
When conducting peacekeeping operations with limited numbers and resources, your aim is not to make the peace, but to de-escalate situations wherever and whenever possible, and shoot back only when you have absolutely no other options.