Hi Daniel,
you are right: the build 4686 works like a charme with Play.
Your previous procedure (scenario #2) needs to be modified, though. You get that error just because you need to switch on the VE Pro Engine (the first icon in the toolbar) BEFORE loading the Play VST. If you do that, you can use it right after you opened it without the need to close it and reopen it.
Now my problem is that I cannot open my old frames (both VIFRAMES and MFRAMES) with an the old version 4686. The message I receive is "Could not load the plugin". Are those files that much version-dependent?
Unfortunately, I need to reinstall 4881 as I don't want to build a template with 80 instruments from scratch!!! [:P]
I hope VSL can fix that problem. There's no reason why a plugin can work in 4686 yet not in 4881.