This suggestion allows players to 'create' their own mines and herbs. First thing I'll say is that this needs to be done carefully to avoid unbalancing existing availability. These should be at the end of the existing research paths.
Herbs
Either (a) a sov building that produces herbs directly, or (b) the ability to send Herbalists out to a terrain square to attempt creating a plantation. I'd favour (b) as it allows people to exercise a range of military protection options, especially if we create a rule that you can't harvest (or you get a very reduced opportunist harvest) off enemy/neutral sovereign ground.
Success of a plantation depends on a number of factors, e.g. the number of herbalists sent, the length of time they stay (we'd need a 'tend' option with a duration, to supplement the existing gather'), and the terrain. The planting mission would need a stock of the herbs to be planted.
Mines
The idea is that you send someone out to survey/prospect a square, in the hope of finding mine-able resources. Success depends on the same factors as for herbs, above.
Would miners be suitable for this, or would we need more 'specialist' units?
Edited by Albatross - 30 Jan 2013 at 14:18