Ironically this is accidentally begging the question - that breaking them up into LLM context windows would be good because it would be to fit them in LLM context windows.

Maybe you're right but I'm aghast at how much of engineering over the last 15 years has been breaking up working monoliths to fit better within the budget of an external provider (first it was AWS). Those prices can change.

There are good reasons to use microservices but so often they're used for the wrong reasons.