Thanks for your thoughts. Yes, Virgin Express would be considered a point-to-point and there would be no checked bags involved so that would save some time. Also, I double checked and there would be just over five hours connecting time, not the 3-4 I previously wrote. The way back would not be a problem because they'd be in Brussels the night before.
I wrote to "Ask the Expert" on onetravel to get his thoughts also.
This is what he responded with:
You have given yourself enough time to make the connection, and since VS and BA/AA are such great adversaries (The tail of VS 747's says "BA/AA No Way" as an anti merger sentiment), it is my bet that VS would go out of their way to accommodate you ...
I do the same trick all the time and even the one time I was late, a simple explanation was all it took. Remember, tell them your problem and let them solve it. Suggest but let them come up with the solution to your problem. It is human nature to want to help.
I've done this quite a bit myself and haven't had a problem, at least not yet, but I'd hate to suggest it to family and friends and have them experience difficulties.
OTOH, if they had to buy a ticket that day it probably would not be more than the savings they initially realized ... so I'm not sure that they have too much to lose. Hmmmm