A couple of points of view from some of the above:
MAX deckers - I cannot be the only one who thinks refurbishing 13 year old ex London stock, for a premium route, just doesn't make sense. I'm sure it's been previously mentioned these vehicles will have spent their lives dawdling around at 20mph, then they will be expected to be thrashed within an inch of their lives, without any kind of mechanical upgrades.
21/21A/X21 - Although it is classed as an Eco route, that is only the Darlington EcoCity operated 21/X21 portion, I think any upgrades will come in the form of new vehicles for the whole service, Streetlites would be ideal. 4812/13/14 have started to suffer from reliability issues lately, possibly their role as pre production demonstrators is starting to catch up with them.
X75/6 - I don't think it will be advertised as "Limited Stop" but there are large portions of the route where there are no stops to serve, so I think that's where the reasoning behind the MAX branding comes from. However, I think other vehicular alternatives should be sought for this route.
Destination screens - Don't get me started!!!!