I don't know...
It seems to me that AwareIM was designed to work just like that. I don't - I have two licenses but I think you could depending on how much user activity you have and how much processing power. No question that your development work would impact general user performance but it's worth a try. Budget is your real problem. On a low budget, you will always be scrambling for resources, but I think it's possible to resource a machine sufficiently to work in the Dev\Production model.
I can recommend Amazon Web Services which is where I host production. Start with the most meager machine and then scale up as needed.
I use two licenses as you describe; one for development and one for production. I use the Professional version in production and the Developer version in development. It seems that the Professional license supports whatever you give it, but if you want to develop with developer features, then you need it at least for development.