remote connection and graphic problem
Buy the dongles. I worry your company is able to secure these if it isn’t budgeting for training and support let alone very inexpensive adapters. 

There’s being frugal and then there’s “we’re not even thinking about selling one Mac” to fund to what needed to run the rest of the fleet. 

If your labor is cheap, make cakes and cookies and sell them to fund your business. Good luck, I don’t mean to insult, but the reasoning in your question doesn’t add up. 

Also, solve your network issue - the business and you are toast if you can’t get control of the network (we’re back to security and priorities).