In some places (LHR, CDG, FRA), yes you are crazy. Last summer there was a travel embargo (in some dates, and these are just the European destinations I remember) for LHR, FRA, and AMS for buddies. If you choose to do this, you definitely (moreso than employees and their dependents) need to pick dates and places. Come up with probable dates you'd like to go and check flights leaving in the weeks before to see how they look (if it's the middle of July and LHR looks good now and two weeks from now, odds are it will still look good in two weeks). Saturdays are actually a decent day to travel

BRU usually looks good, and MUC does on some dates (moreso than ZRH). You might want to consider MUC as they have the new ORD-MUC flight, which will probably be decent.

As others have said, it would most definitely be better to buy tickets for summer. The cost to the employee isn't much less than an advance Y ticket. Save the buddy passes for Jan/Feb when you can choose where to go and get there in C. I don't know of any employees that have been stranded although buddies almost always seem to be stranded