It's an interesting idea, but it would be costly. I suspect at the end of the day it would probably be cheaper to build a Lunar satellite that retrofit ISS. Basically you would need to add a lot more shielding, and I have my suspicions that would be difficult to accomplish.
Honestly, while it doubtless costs and will continue to cost a lot to maintain, maintaining it is still cheaper than (eventually) building a new orbiter. Obviously there are finite limits to how long anything habitable can remain in space without significant overhaul, but as the article says, 2024 is a policy limit, not an engineering one.
As to a lunar orbiter, I think it's a damned fine idea. Figure out how to build it in modules, and have robots or remote control piece it together. If you could get that kind of technology down pat, you could basically build orbiters for Mars or beyond, send them ahead of any manned mission, and thus you could significantly decrease the amount of supplies needed for the actual manned mission itself.