NASA May Let Billionaire Astronaut and SpaceX Lift Hubble Telescope

Boost. The term is boost, not lift. This isn't a helicopter.

I understand the term 'lift' may be more accessible for the general public, but it drives me nuts to see news outlets use it.

https://archive.ph/tlo1V

We already have standard docking adapters. It should be straightforward (engineering-wise) to develop standard space tugs to act as prosthetic attitude and altitude controls. Only a matter of cost. But surely it's cheaper to extend an existing telescope vs launching a brand new one.

±required maintenance, materials and sensors reaching their end-of-planned-service-life dates.

I'm not so sure it's "clearly cheaper" to extend the lifespan of a vehicle that's approaching the end of it's planned service life.

Anything mechanical for the sensors will wear out over time. And from playing quite a bit of KSP, bolting on attitude control after the fact is a hell of lot harder for any precise movements since you throw CoM off.