They are probably planning to reuse lots of parts from model 3 to save money
And people are creatures of habit and highly social so version 1 of robotaxis will 100% look like normal cars. Regardless of whatever benefits you can come up with on paper. Once it's normalized then you experiment.
This is the company that released the CyberTruck. V1 will probably look mostly like what was presented. Every single prototype they have ever unveiled eventually ended up looking very similar to the production model.
And people are creatures of habit and highly social so version 1 of robotaxis will 100% look like normal cars. Regardless of whatever benefits you can come up with on paper. Once it's normalized then you experiment.