It doesn't say in the BA ops manual you can land on a runway with an aircraft blocking it. It also doesn't say you can't. pilots are selected and trained to use common sense and judgement to maximise safety and efficiency.
All things being equal if the revised LDA at ACC was greater than the ED at the alternate, provide consideration was given to GA profile then it seems ok to me.
Before I landed I'd consider the problem for the crew getting the jet out of there however.
Sound thinking.
If it happened to me, I'd want to find out:
- Where and what the obstruction was.
- Whether the runway had been inspected/swept since, in case bits had come off the aircraft that came to an unscheduled halt.
- What minima were appropriate, e.g. if it was in front of the LOC array, an ILS probably isn't going to work.
- What landing / go-around performance was required.
- Was fire cover back to acceptable levels.
- As above, will there be issues for the next sector.
If the answers were satisfactory and the required aircraft performance came within the normal operating bracket in terms of safety margin, etc. then having discussed it with the rest of the crew and tech. management / performance if I could get hold of them, I'd have no hesitation to carry on to land or even commit to destination.