There are issues with forcing upgrades, as this can break customer sites if they are using old plugins, but there's the problem.
Unfortunately restoring a backup will put the site back into the vulnerable state it was prior to the compromise, so if your not willing to upgrade then your site will probably get hacked again.
We do try to get our customers to upgrade, but have now implemented an automatic patching system, which detects and patches vulnerable files, rather than forcing a script update.
So far this has been successful and we've seen fewer and fewer attacks hitting their targets, as the vulnerabilities have been sealed.
We basically send out emails like.
"We've found the following Vulnerabilities in your account.
List of files and issues
If you have not fixed them in 24 hours, we will patch them for you"
So we are saying you have a choice, you fix it, or we will.
I bet you can guess what most people opt for.
I suppose we are therefore trying to pre-empt the compromise, by hardening their software installations.
If customers don't want us to patch it, then they can look at it themselves, or even restore a backup in the R1Soft plugin, as we will have told them when we patched it.
Again though if vulnerabilities are put back, the system will repatch it.
This in our eyes is better than the suspend the customer after they are hacked. It's a little more pro-active.