Yes, I can see the siding causing problems, tbh I'd forgotten about it. As far as I can tell it's mainly used as a passing loop to hold northbound freight trains during peak periods, but I've seen long ballast trains parked there for a couple of days in anticipation of permanent way work. So it could be an issue.

As for the sightlines on expresses, hmm the absence of any reported incident on the crossing suggests it isn't anything like the problem Network Rail want to portray it as. But I think NR were probably over-reacting to the Enfield incident and got caught out closing a popular crossing without any plan to replace it. So all the justifications were done after the fact to cover their backsides.

keep to the Fen Causeway