Suggestion - Give Wage Cost Reduction as a Rewards on higher Levels of Jobs in Kingsmarch

I have seen a couple of Posts about increasing Gold that drops in Maps and other suggestions, but I did not see someone bring this up.
It would Reward us for Upgrading everything in Kingsmarch to max. Think of it like smeething speed just "10% Wage Cost Reduction" or "Miners Cost 10% less Wage".
GGG could even slowly add this maybe they Patch Monday and its like 5% if you level the Job to lvl 6. Week 4 could add another 5% at lvl 8 and maybe after 6-8 weeks a final 10% for lvl 11.

Maybe this has a downside that I'm not considering?