Its one of BA's oddities, the answer will be no.
I've arrived 9hrs before a busy flight before (connecting separately, hence the big time gap) and BA will risk noshows rather than moving a proactive flyer making a change request.
They offered to accommodate with a change fee and fare difference, of course, at a huge sum. Obviously I declined, had breakfast and lunch in the Cathay lounge, slept on the secret sofa for 4hrs, grabbed a shower. And even after all of that - at further cost to BA somewhere along the line - the busy flight had to bump pax anyway.
Could have been simply solved by moving me at my request 9-ish hours earlier. But it's not the airline's business practice.