Depending on your budget level, you could try using something like vRealize Automation to allow them to spin up new VMs (from a set of templates for their use) as needed (with approvals for anything over certain parameters). If you have no budget (or it's worse than going for a root canal to get approval) then we'll need to get more creative. Depending on how many developers you have molesting your environment, and how many VMs they have, you could have some options. One group at the software company I worked at last had several VMs based off the same VM, with the same name and IP address, but with different software versions on them (for the company software). They would simply power on (and off) the ones they needed to use. While it might not be AS fast as using snapshots, it was very trouble free. It could consume some more storage, depending on how many VMs they actually need, but if they don't need high performance, just go thin provisioned. If they want more VMs, then get them to pitch in for more storage capacity to fill the need (with room to spare).
It baffles me how some software companies want all these capabilities, to use VMs, but when you tell them that because they're using three times the amount of resources they originally claimed they would use, that more needs to be purchased. Then they cry poor. Meanwhile, they're spending thousands, each month (or week) on other crap that is a waste of funds.
