I think that officially, if the change is under 2 hours, BA's official policy is that it would not entitle you to a change. However, in practice, I have found that if the request is reasonable, you could ask to change for another A-B-C itinerary. This would likely need to be approved by a supervisor but would probably be allowed in most cases if the same booking class is available. This may also be affected by status, previous travel incidents, etc. In my experience, a change of routing is unlikely to be accepted, but again, that will be assessed on a case-by-case.

So the official answer is the most negative, but there are ways for agents to occasionally request that exceptions be made on a case by case basis. It does not need to be "consistent" because it is precisely a matter of discretion which is better for all involved, because the alternative to that is to stick to the restrictive official provision.