Replacing the 73TS before the 72TS makes sense in a way - the primary objective here is extra capacity, not just nicer trains to travel on. I imagine the bathtub curve will put paid to any significant reliability improvements before the 2030s. The Piccadilly upgrade is cited as providing a 60% capacity increase at peak times which is definitely needed. The Bakerloo upgrade, apart from being a less significant 25%, is also from what I've seen of the line's usage, less urgent. The only urgency really is the rather dire state of the trains. The differing quality of the refurbishments mean that for the 2-4 years difference in age, the 73TS looks as if it has 10+ more years of service life more than the 72, but for the reasons above I can settle for them being done in the opposite order.
What I'm less happy about is the wholesale replacement of the B90/B92/B2K DLR units before the Bakerloo stock. The performance and reliability of those units to my knowledge would lead to very minimal benefit in them being replaced other than the small area gains from being fixed-formation units. With no cabs to get in the way, that's probably less than a 10% benefit. I'm all for new units being introduced to ensure all DLR trains are full length and to get some air conditioned DLR stock, but I'd have thought the Bakerloo upgrade really should have come first unless they spend a very large sum bringing the 72TS up to a reasonable standard.
The 92TS are also very tatty from 25 years' heavy use without refurbishment (the seat cover and cab change a few years back doesn't count!) - I'm aware that they're rather unloved and being left to deteriorate prior to replacement but for a line as important as the Central line and with 10 years before the first unit gets withdrawn, I really do hope they at least give them a refresh, a la 96TS. Ideally they'd also fit PIS displays as it's kind of absurd that the Central line of all lines still doesn't have them.
Has anyone been able to gleam any info regarding the ventilation on the NTFL units? I notice while originally touted as air-conditioned, all the blurb about them now reads 'air cooling'.