I’d like to meet Marc Brunel (father of Isambard Kingdom Brunel). He started the second stage of the industrial revolution by inventing a mechanised production-line (it was to make rigging parts for the Royal navy). I would like to ask him if he foresaw how big an effect his idea would have.
There are probably loads from history, but I’d really like to chat with one guy who is still alive! That would be James Dyson. Although I’ve read some of his books I’d still have plenty to ask him, particularly what visions he might have for technology in the future.