so one thing I would like to point out, which came about as a question about me removing the mid row seats to use my van for delivery, is that the reason that toyota quit offering the factory access seat option is because the mid row seat now contains airbags. Its also the reason why they don't easily come out. The new 2021 and 2022 Sienna's that I have personally seen that were converted to mobility vans(2 by Braunability, 1 unknown) were really hacky and really sketchy.
For the Braunability versions, they just took the mid row seats out, took the seat rails out, slapped down a sheet of steel over the floor, and then ripped/cut/hacked the console. The hybrid battery vent was covered, and since the hybrid battery lives under the drivers/passengers seat, and needs the airflow, its gonna die quicker or not work as well because it won't get adequate cooling. The quality of the work done was just shoddy, like, really bad.
Also, with no mid row seats, I could not even suggest you put people or stuff in the rear, since the mid row seats contained the airbags for the rear seats, it cannot maintain its crash safety rating with the midrow seat bags removed.
The other mobility one I saw was a "rear access" type, im not sure who made it, but like the "freedom" company one, they literally pushed the midrow seat rails out as close to the door as possible, which means the front seat mounted airbags for the mid row passengers will not be in the right place! They also cut out a huge section of the rear structure of the van, and it looked like someone who was not experienced with welding aluminum went after it with the wrong type of rod, because it wasn't pretty, and looked like if it got hit in the rear, it would fold right in the middle of the van like an accordion.
TLDR: the braunability looked better, as it did not modify the structure of the van, and the floor was at least not cut to pieces, but the drivers area left some quality work to be desired. the rear access one honestly looked like it had compromised the safety and structure of the van to the point that it would be a safety hazard to be in an accident.