Make the AI build mining BASES. The maintenance is lower, and you don't need to issue any 'order' to make them stay put.
You just need a minister smart enough to check them every turn and see if they are 'making a profit' or not. When they cease to be profitable, send a SYS to scrap them. Are there script functions to check the percent of minerals, organics, and radioactives of a given object or sector?