Thank you!
Which Tesla semi exactly do you mean? I found these two:





However, I thought about making an electric truck some time ago and this would be my favourite:



It's an electric truck made by Thor Trucks and it looks a hundred times better than any of Tesla's semis.

Sure, if you are going to make it public please state somewhere that I made the design ^^
And please take a look at my other taxis. They are so much better (in my opinion) xD

Well, let's think it through:

If you want to get in, you need some kind of door. That can be a trapdoor on the roof or a door on the side of the car. I think the trapdoor is a lot easier to implement. But you also only can use a trapdoor if it fits the car's roof's color sufficiantly. Otherwise it looks odd.

Next, you need at least a two block high room for a player to stand in, or a minecart or invisible horse inside of blocks. This way the player could sit in a one block high room.

To get out, you most certainly would need a ladder somewhere (given we use a trapdoor). If your room is only one block high and you have a minecart or horse in the ground, you could simply jump out (cause it only is one block high).

In fact, you totally could make this taxi accessible. You only need a trapdoor on the roof, a ladder inside and probably more space inside (I decorated it with netherbrick stairs as seats).

So, I would say, it definitely is possible to make a car detailed, get the correct shape and make it accessible. But in most applications it is not needed to enter the car. What often is needed are realistic cars and the single trapdoor on the roof would make it less realistic. That is at least why I didn't make any of my cars accessible.