I cannot see this happening as a spare place to park an a/c costs money. If it was put on show it would encoursge viewers and spotters to the location and i cannot see that being encouraged by BA or BAA. If it is within the complex why would the staff wish to see the a/c when they go into work. By the time this might be in place there probably will be hardly any engineering staff left anyway. Lets hope I am wrong but BA has never put anything on show at LHR, with the exception of trhe tunnel entry.
Lastly this plan has been muted for years and was also at one time the plan for a Trident 3 and look what happened to that (MAN)