VM Hosts: Single Large Host or Few Smaller Hosts?
A good rule of thumb is to try and avoid using one bit of logical kit (be it a single VM or a single physical host) for more than one thing.

If a physical server is going to be a VM host then that's all it should be. If a VM or a physical host is going to be a source code repository then that's all it should be etc. You can squeeze a bit extra out of your infrastructure if you consider everything to be a VM host and you then partition up those VMs to be single purpose hosts themselves.

The rationale behind this is that


A single host going down shouldn't impact your entire stack. Trust me this will hurt you badly as soon as you need downtime for an upgrade.
The cost to scale any individual component increases drastically if you want to try and scale on multiple similar servers (which will save you management dollars by reducing complexity) or it will cost you to scale out adhoc hardware as needed because you then need to deal with many different-sized hosts that are a pain to manage and require anyone managing them to know the platform intimately.


recommendation: split your infrastructure into as small a unit as is logical. If you can only afford to buy a single large bit of kit then make sure you split it into logically separate VMs or containers so that if you need to pop a bit of your infrastructure onto another server, or you need to scale stuff at different rates you can easily expand out but investing in a smaller upgrade.

Obviously the realities of software licencing, especially for windows OS's might make this cost prohibitive but, while I haven't caught up on windows licensing models in a while, I'm sure there are development centric licensing models that can suit your specific needs.