Would be nice to be able to upgrade settlers speed and capacity. Like:
-lvl1 upgrade: carriages - settlers return goods after 2 rounds in workyard,
-lvl2 upgrade: carriages+horses - settlers return goods after 2 round in workyard and travel 1.5 times as fast,
-lvl3 upgrade: carriages+horses+(some special item?) - settlers return goods after 3 rounds in workyard and travel 2 times as fast.
Upgrade all of the working settlers at once or upgrade only some in the workyards they work in.