I am playing right now… and you know, i think the only 1 obj at a time… is really an issue… it is utterly boring to be in the situation where an obj is obvioulsy blocked.it lead to brainless metagrind behaviour… whereas in reallity when you face a wal. usuallyu you try to get around it… change your approach or even completetely change your objective for a time… now we just cant do that… and we are doomed to go to the wall that is a big issue i think 
And your CS example is saying the same actually ( 2 obj to choose from) if one is overcrowded lets sneak to the other !
Another note… when (hopefuly neveror not often ) we are facing only 1 objective then we need SIDE routes… and for the record… a side route is NOT another route to get to the same “line front” rather we should calle them BACK routes because they have a meaning and a utility if the lead to another front line and or to the back of the defense…
for instance in waterloo the pump is NOT a side route… it is a somewhat “shortcut” to go faster on the same frontline
but it doesnt offer any new dynamic to the game nor change the line front … so it is basically useless 
same goes for the side door on trainyard… it leads to teh same location and doesnt change the front line
another useless objective and not a real SIDE