New unit: Farmer
Along with this unit should come a new flag: the farming flag. As with the rescourec destruction flag, you can set which rescources are 'active'.
The farmer glob will try to harvest the specified rescources from the nearest spot, and replant them at the designated farming spot. Also, farmers passing near crops cause them to grow faster (while the farmer is near).
Different flavours of units with different affinities can be sorted by these very affinities.
I.e. when AI assigns a job and there are both "Forager" and "Builder" free, all it needs to do is to look up which one have better ability for this job and prefer it. Amount of micromanagement needed: zero. Amount of running around: slightly higher, but once they'll start doing what they do best, they'll tend to stick there, so in the end it's not a big deal.
I would be more after robartsd's proposition to farm. More specialisation is 1) more micromanagement, 2) more difficult and complex to code
But to be sincer, I like farms the way they are now.
I think it is best not to over specialize the types of globs, but a way to define a farm would be good. Here's my idea: