I've been reading some of the excellent answers on this question about galactic empires and it led me to imagine a reasonably realistic multi-system 'empire' might keep most or all of its population within a single system and have a presence around other stars only for the purpose of harvesting their energy.
The most naive conception of such a scenario would be to have a dyson swarm of some description around each exploited star (built by self-replicating robots) and use lasers or microwaves to beam the energy back to the Sol system. This energy could conceivably also be used by a sufficiently advanced society to produce matter in a kind of long-distance stellar lifting - my back of the envelope maths puts the energy output of a Sol-like star as sufficient for ~4.3 billion kg per second before (likely considerable) efficiency losses.
My crude calculations (based on this data) suggest that even with only 1% overall efficiency a single star could supply raw material equal to almost eighty times the total mining output of humanity in 2017, though I have no idea how optimistic (or otherwise) that 1% figure is or what proportion of human resource consumption is represented by mining.
The biggest question for this proposal is whether or not it's actually feasible to send energy on this scale across interstellar distances reasonably safely and without it dispersing so much as to be infeasible to collect at the other end. If it is, what's the best way to do so and what would that look like?