I just made up a term - the waiting time at calling points (e.g. Stafford/Rugby) and pathing/engineering allowances may have the potential to be minimised.
From December, there is essentially zero slack.
The standard hour southbound path from Crewe is
xx13 and has no pathing at all. The only dwell that's longer than 1 minute is Rugby, by half a minute. So in theory half a minute could be cut out of the schedule, except that that would just be rounded up anyway.
The standard hour northbound path from Euston is
xx46 and has half a minute's pathing. The only dwell that's longer than minimum is Nuneaton, at 4 minutes. So in theory 3.5 minutes that could be cut out, but it's clearly been added in because a slightly earlier path wouldn't work further north.
The new December paths are very good overall, although I must admit I'm a little bit concerned about the reduction in the turnround at Crewe (now just 19 minutes) and the close proximity of the xx13 departure to the xx10 departure of the TfW Manchester-south Wales service (which is frequently delayed, due to the short turnround at Piccadilly as well as being held to cross the layout to get to Crewe platform 6).
The engineering allowances - 4 minutes each way - aren't unduly generous in my view. That's just 3% given a journey time of about 2 hours - the Swiss railways (as well as some other parts of the British network) use 10%, and it shows in the punctuality statistics. The one thing that doesn't make sense is Sundays, where for reasons best known to Network Rail, it has been decreed that an extra minute's engineering allowance is needed between Euston and Hanslope Jn - even during the (few!) hours where it's planned as a 4 track railway. This is at least a reduction on the current 2 minutes extra, but it's still nonsensical.