I am entirely in agreement from my own experience that centralised remote deicing appears a superior method of operation compared with on-stand deicing. There may still be queues at the deicing area but it means by definition that aircraft have vacated their stands. Also the route of the deicing trucks is simplified to and from the fluid storage facility rather than have to continually reposition to different stands. Some airports also used fixed gantries and supplement them with deicer trucks.
Location might be an issue at LHR but I suspect if the determination was there a way would be found. I cant help thinking the T5 development was a lost opportunity in this respect and this appears to apply to the ongoing Central Area redevelopment.