Would Toyota have any chance if the HiAce gets some US-spec versions?

Certainly one of the most successful among all modern commercial vehicles, the Toyota HiAce is by its own merits a common sight in many countries, even in my homeland Brazil despite never been a captive import here. As it shares many mechanical features with the traditional body-on-frame trucks and SUVs range from Toyota, including engines and transmissions, seems quite straightforward to certify for compliance with the American regulations regarding fuel efficiency and emissions, while a switch from cab-forward to a set-back cockpit in the 6th generation is part of a broader approach to increase the crashworthiness which also prevented the previous generation from having its US-spec variant. But now it's quite a good time for Toyota to eventually rethink its strategy and at least give the American van market some attention, also considering how overseas models such as the Ford Transit and the Fiat Ducato rebadged as RAM ProMaster took it over from its former orientation toward a more conservative design mostly shared with full-size trucks which are still leading the USDM as a whole.

Possibly one of the fewest changes unrelated to safety or emission regulations I could ever consider to make the 6th-generation Toyota HiAce more appealing to Americans would be replacing its rear liftgate for a barn-door setup, much easier to carry palletized loads with a forklift and a better height clearance while loading or unloading a stretcher in an ambulance conversion. Even though general export versions of the 6th-generation HiAce may eventually differ in lenght, wheelbase, overall height and even width, yet holding my breath for the narrow-body SWB model with a low roof, set to comply to a Japanese regulation which attracts a lower annual tax for so-called compact vehicles which goes as far as including commercial vehicles, is out of question, despite it eventually becoming a better choice for certain operators in some crowded metropolitan regions. But anyway, as Toyota can ultimately benefit from its worldwide economics of scale, despite the Chicken Tax which could apply in case some US-spec variant of the HiAce would be made outside the NAFTA zone which also includes Mexico and Canada, and since Mexico is not only less strict regarding safety and emission compliance enough to eventually justify the HiAce becoming also made there but is also a major export hub for motor industry, I really don't know what Toyota is waiting to finally place a bet on the USDM with the HiAce.

Are dune buggies the vehicle category facing the fiercest competition?

Having been usually built upon repurposed Volkswagen frames from models such as the Beetle, dune buggies used to have a much broader appeal in Brazil prior to the market reopening for imported cars, which brought modern SUVs and turned them into the new craze among the urban Brazilian middle and upper classes. Safety and emission laws also rendered it harder for buggy factories to keep a full production volume, even though the usage of as many components from some mainstream cars as possible could enable the economics of scale, to the point that now ABS brakes and even dual airbags can be fitted to some buggy models in Brazil, not to mention the downsizing with turbocharged 1.0L 3-cylinder engines replacing the EA827 and EA111 engines which themselves were a replacement for the venerable air-cooled boxer engine once Volkswagen phased it out. But the traditions which made buggies retain a foothold on the coastline of the Nordeste (Paraíba/Bahia/Ceará) region were not really enough to be an effective contender to other categories such as compact hatchbacks and sedans which are still prevalent within the entry-level segment in the Brazilian market.

The absence of comfort features formerly regarded as a luxury such as power steering and air conditioning, or even a basic forced ventilation which may be redundant while driving without the canvas top yet actually quite handy when a pouring rain makes the "winter top" a must even on summertime, is harder for an overwhelming majority of the Brazilian car buying public, so not even the predictably low manufacturing cost of a buggy bodyshell would render it suitable to address the needs and preferences of most new car buyers in Brazil anymore. Despite it also being possible to fit some cargo restraint devices such as racks, in order to eventually serve to the same purpose of a regular car, the practicality inherent to a hatchback or a sedan turns them into a safer bet, while a dune buggy is now mostly seen as just a curiosity on a trip to the Beach Park in Fortaleza. So, while it could be eventually possible to rely on a dune buggy as the only motor vehicle for a household, and resort to minor adaptations to enhance its suitability to the task, a fierce competition not only against a strictly conservative economy car but also against SUVs with a clearly focus on the recreational usage are quite hard to overcome...