I've been using automated fuel harvester ships this game, with the conditional order: fuel tank full -> harvester transfer and return. This works well, but there are a couple of niggles.
You get warning events when the fuel tank is above 90%. Which basically means you need to hide that event because it just spams repeatedly. I normally use these events to manage fuel harvester stations - sending a tanker out to the FHS fleet whenever its needed. So I can only use one type of fuel harvester or the other.
Suggestion: Suppress the fuel over 90% event for fleets that have a conditional order with a fuel tanks full trigger.
The harvester fleets still generate Order Complete events when arriving back at their gas giants, which is a mild irritant when I've got many FH fleets - I pay attention to Order Complete events for managing my fleets generally, so seeing ones that don't require me to take action is a distraction.
Suggestion: Suppress order complete events for a ship which has a conditional order set with trigger: fuel tank full, and action: harvester transfer and return, that has arrived at a gas giant with sorium. Maybe get really fancy and if a ship with that conditional order finishes its orders anywhere that is not a gas giant with sorium, generate a "Cannot Mine Here" event, which would be handy for spotting when sorium is depleted.
Bonus Suggestion: I think harvester transfer and return is an 'S' order, so can only find a colony within that system to transfer its fuel to. Personally I'd like it to be an 'A' order, so I could mine in systems I don't have a suitable colony in - be handy for keeping fuel on hand at a colony in a system without gas giants.
