] I thought he meant that she may drive her son to some desperate act, even suicide. At least running off to India or to sea to get killed in action.

I'm not sure how dangerous it would have been to be an officer serving in the East Indies at that time, but I have often wondered if that might not have been part of what Brandon contemplated in securing his exchange overseas.

I thought that Emma Thompson's take on it, where Mrs. Jennings tells Elinor that Colonel Brandon might have 'done himself a harm' if not for Sir John is a plausible interpretation of the situation and his personality.

Even if he might have had a 'death wish' of sorts, I have trouble seeing Colonel Brandon as a man who would contemplate suicide. On the other hand the comment that he makes during his 'confession' to Elinor about Eliza:

"...happy had it been if she had not lived to overcome those regrets which the remembrance of me occasioned."