I wonder if one practical measure would be to require controllers to inform IFR traffic when it's about to enter Class E airspace? At the moment there's no requirement to do that, so a heavily-tasked pilot in the arrival phase in a busy TMA who is transitioning from Class A to Class E is given no reminder/hint that his/her lookout and crew resource management might need to change. Yes it would require an additional ATC transmission. But isn't that better than the risk of a collision?
Isn't airspace structure something to discuss during he TEM part of the approach briefing? The information is there (AFC in the LIDO world). And for someone operating the first time to an airport with that kind of structure and/or frequent glider traffic around that information should be part of the destination briefing package.
Of course, some airports do give information about gliders, listen to EDDS ATIS on a nice spring/summer day and you notice quite a bit information about glider sectors. And you might notice that that information is for VFR traffic as IFR will be separated from those sectors anyway.