So, basically, you want the length of the calendar day to sync with the actions of the units on the map, as opposed to the length of the year.
I suppose we can't have both, without the year getting ridiculous long, and this does seem like a pretty well reasoned compromise, with dwarves sleeping once a day, etc.
We manage to cope with the current system when it has many serious breaks from reality. This proposal seems to have fewer.
There are some balance tweaks that would need to be made, for this to work, possibly a lot of them.
Liaisons might need to stay longer, in case your broker or mayor was in the middle of one of the longer jobs, when they arrived. It can already be a pain, getting them to put down what they're doing. --or we could just have dwarves cancel jobs, if they conflict with a meeting. It's sloppy, but it would work.
Weapons production would become a lot more important, in the early game, as you'd need to start as soon as possible, to have a hope of getting any done, before you needed them. This isn't necessarily a bad thing, and gives some weight to wooden shields, and other military gear that doesn't require a strong industrial base.
The production rate bonus for skilled workers will mean a lot more, and there will be an incintive to assign multiple dwarves to a single labor. Currently, you quickly reach a point where anyone other than your furniture and weapons industries can be manned by a single dwarf, in a fort of almost arbitrary size.