One of the reasons I'd like to see something along these lines is that the early part of a fortress is pretty same-y. Apart from occasional kobold thieves or hungry animals (both depending on location) there's not much to slow you down as you set up some farms, build some workshops, churn out 10,000 stone mugs and buy everything from the traders.
Later on in a forts life you have goblin ambushes and sieges, uninvited guests and horrors from the deep. Plus the increased noble mandates and the (broken) economy.
I'd like to see some challenges in the earlier years of a fort too, at the moment it's extremely easy unless you deliberately handicap yourself (hermit challenges and so on). I think having to divert some dwarf-time and resources to pleasing the Mountain Homes could provide some extra difficulty and maybe you won't be quite so ready when the first goblin attacks come so they wouldn't be such a walkover.
If for example you are on/in a mountain they should not ask for wood.
The game should already know what kind of rocks, gems and wood is available for your embark location so having contextual mandates shouldn't be a problem. And even for goods you don't have naturally you can trade with other civilizations. Also having to supply something like soap would mean you need to set up a soap economy much earlier than you might normally, making forts a bit different early on depending on what challenges you have to meet.
As for the cost of an expedition, the 'points' you start with don't seem like a good indicator of the costs of preparing a group of dwarves with equipment, supplies, animals and a wagon. Bare in mind that the food you 'purchase' is what you arrive with, anything consumed on the journey, the wagon and work animal are not included, nor are the costs of the dwarves themselves, just their skills, they aren't even getting paid for their work.
You'll probably have to deal with taxation eventually.
Taxation doesn't seem like much of an issue seeing as your forts all end up becoming the capital, plus we don't even know if these dwarves have a completely feudal system; the baronies and duchies may not collect or pay tax. The economy we've seen didn't include tax, just wages, goods and rent.
"send 50 copper mugs" button every year to avoid a -10 happy response from the mountainhome.
Pretty much everything in DF now is an 'x' or 'y' lowers or raises 'a' or 'b', with the hope that one day it'll have more of an impact. Now development is moving in new directions we'll see more of those interesting things added. And more diverse challenges and game play options would be good.