I can see Dyson having lots of fun trying to find the available engineers. Jaguar-Land Rover has been busy sucking up automotive 'talent' in the UK for the last few years.
I wonder if he will try to do the whole project in-house or try to utilise the existing automotive supply chain. Hopefully, the latter.
Modern cars are not just power-trains (although that's a big part). User's expect toy's like entertainment systems, comfy seats, controls, parking aids, etc. If Dyson wants to play at the top of the market then he needs all those toys. That complexity isn't cheap to develop from scratch.
The whole vehicle has to be tested to meet all the regulations. Depending on which countries you want to sell it in, there may be multiple regulations to meet (for instance devices containing a Bluetooth radio have individual approvals for each country).
Some of those regulations he will have come across with his other products, but there are new ones also.
Personally I think his timing is optimistic.