That makes a lot of sense. You could even have things decay that you can't support, like a warband that does less damage for lack of metal or walls that are weaker or buildings that eventually collapse. Malnourished workers might process resources more slowly. You could get natural ruins that way, as well as potentially annexing holdings into an empire that cannot completely support it, forcing you to choose what to neglect. It might be useful in such a situation to have the option to deny resources strategically.
Anyway, I'm rambling now, but I like really like the idea or placing more focus on maintenance. I think that could scale very well and provide for many interesting decisions and circumstances. Thanks for letting us in the process here, can't wait to see where you take it.