You are right on all points. You can't do this with the crowd. I get into the show at least an hour before the public is allowed in, usually, while the cars are rolling in so I can stand back far enough to do this. If you try it with the public wandering around there is always someone in front of you if you stand back far enough to shoot the entire car profile at 50mm.
After I take all the shots I need, often with the OLY 14-150 - because the long end is handy for some shots, the range is convenient - no lens swapping, and 28mm is wide enough, I'll get close to the hood ornaments and position myself with the backgrounds I want, and take those with the same lens.
The 14-150 is as sharp as a PRO lens at the short end, not at the long end but for a car show I don't need feather detail or shallow DoF. People want everything in focus or close to it. They want to see what's on the show floor. It's what the event organizers want. - The show, not art. Take one art shot for the poster if they didn't pay someone to paint one. The trick to this is the 14-150 will focus on a hood ornament a few inches away and a car 100 feet away. It's an incredibly useful zoom range when you don't need the sharpest, fastest lens.
Now with the show covered with a single lens, I'll pull out the 25/f/1.8 and look for interesting thiner DoF opportunities. Then if the show field is wide and I want to try for a shot of all or most of it I'll pull out a 7.5mm f/2.8 MF fisheye, put the center on the horizon, set it on infinity, crop the top and bottom and it looks like a 7.5mm wide-angle image. Or if I don't feel like bringing that lens I always have the silly OLY f/8 fixed aperture 140-degree fisheye - 9mm and use that. A body cap lens no other professional would use, it makes me smile. Cost me $50 and makes good images. The center is decent and with a wide-angle lens and IBIS, f/8 works great. For what ends up to a be a wide-angle landscape you want deep DoF. Sometimes I'll use one to photograph auto interiors. I usually don't need to defish it. Some look cool as a fisheye.
This is not a maximum sharpness or artist use case. Light is almost always good. If it's an outdoor show it's canceled in the rain and if not there is still enough light and it's fun shooting cars with raindrops falling on them. Indoor car show lighting is usually very good.
This use case isn't about max IQ or shallow DoF. It's about entertainment. You can use a cellphone but it doesn't have the reach. I can do this with an EM-5 1.0 or an EM-10 1.0. 16MP is enough. 10MP is enough if you don't have to crop much and with 14-150 range you don't. The 25 f/1.8 and a fisheye spice it up a bit. I don't use them to shoot an entire car or an entire show. Even when I use the 25 a lot I usually pick many more 14-150 images for an article. They show more of the event and put more of it in focus. Deep DoF is GOOD.
I get close with the 25 so once the public enters the show floor it's OK to have people around. Thin DoF is useless when the subject is far away. The result doesn't look thin. You could shoot on infinity.
A show floor is more interesting with people on it when I'm using the fisheye for a wide-angle shot. Sometimes I remount the 14-150 to take candids of people. That's at the very end when I have everything else.
I can do this with a 2.1MP OLY C2100 compact camera on "P" that I used ~ the year 2,000. I need to do it for grins. The camera still works though most of the memory cards have failed and ISO800 is worthless. Even with a range out to 280mm it's a small camera. The sensor probably fits on the head of a pin. The optics are excellent. Internet magazines are happy with 2000 lines horizontal. They will take down to 1500 lines and less if they have to if they like the composition. Their customers look and move on. They don't; think about image quality or detail. If it looks good, to them it is. They are busy looking at the cool ornament or the impressive Packard. If it's clear that's all that matters. Its what you shoot, not so much how good the IQ is. Many of them don't have a big monitor. This resolution totally satisfies them.
The guys with the high-end Canons, Sonys, and Nikons they take to these shows look at me and might think I'm using a second-rate system. Maybe they are laughing but I've had nearly 30 paid assignments in the last two years. I'm overbooked going into 2023.