The thing that many RC vehicles lack is a driver or Pilot figure. To me, a model vehicle just doesn't look right without a figure to populate the cockpit. Some manufacturers of RC vehicles such as Axial have diligently applied themselves to filling this omission while many more have not.
My vehicle projects range across many scales and I am always on the lookout for any suitable figures that can be adapted to fit. It increasingly difficult to find figures in toy shops that are normally clothed and proportioned they are more usually these days superheroes and come in weird costumes and have ludicrous unrealistic physiques.
The other feature that is needed is the ability to pose them seated. Many of these newer large scale figures from toy shops have no articulation in their arms or legs whatsoever, they cant sit! It means a great deal of hacking will be required and if they are made of high density polyethylene or polypropylene you can forget about it, it's not worth the effort.
Below you can see the figures I have on hand, arranged by scale.
Starting with the smallest on the right, I have a couple of men from a Tonka toy. I dont know where I got these but I have had them lying around in a box for decades. They are 90mm tall so scale out at 1/20th scale.
All my calculations are based on taking the average height of a person to be 1800mm (5ft11). Obviously people's height can vary so a bit of license can be taken where appropriate.
Next to the tonka men is a 95mm figure. This is a common size for these small action figure toys more commonly referred to as a 9.5cm figure. Again I have no idea what this figure is from, I think I got it in a charity shop many years ago. Anyway these figures scale out to 1/19th though you could get away with using them in anything from 1/20 to 1/18th scale.
The figure next to the 9.5cm figure is supposed top be another 9.5cm figure, it even says so on the box, however these figures are actually 105mm or 10.5cm tall this makes them closer to 1/16th scale.
Here you can see a couple of them next to a pair of Bruder toy figures which at 108mm tall are precisely 1/16th scale. They match pretty well and as you can see from the box above are incredibly cheap at $3 from Target. The two shown on the right here are the more normal looking figures, there's a few more in the series but they are a little too freaky in style for my tastes. the Bruder figures are very well articulated and the most normal looking you can get, very versatile if you want 1/16th scale.
Sitting at the bottom left of the pictures above and below is a Tamiya 1/16 Tank Crewman figure who has been hacked to get him from his original standing pose to a seated pose. He is a bit taller than the Bruder figures so he is a very tall man in 1/16th scale.
Next in the line up is a couple of Star Trek reboot movie figures, I believe the one in the maroon jersey is meant to be Simon Pegg as Scotty and the mustard jersey, John Cho as Sulu. These work out to be 1/12scale at 150mm tall. They have reasonable articulation but I have dremeled out deep grooves in their upper thighs to get clearance so they can sit better.
Next along is some toy wrestling figures. I am not all that keen on these as they need some work to clothe them properly. The ones I have chosen at least have pants. At 170mm they work out to be at an odd scale of 10.5 but I figure they are a petite 1/10th scale and I have seen a few 1/10th scale vehicles crewed by these figures. they are nicely articulated but again I have done some surgery on their thighs to get them to sit better.
Tamiya makes a number of driver figure kits from styrene which makes them easy to mod and hack.
The one sitting next to the wrestlers seems to be 1/8th scale though the scale is not listed on the packaging. Below you can see him again on the left with a couple of 1/10th scale drivers. As you can see, the one on the right in grey primer seems to be smaller in volume than the one in the middle but they are both supposed to be the same scale so there is a lot of variation in the Tamiya figures.
Tamiya also make 1/12 driver figures for their formula one sries of model car kits.
What is not shown here is a 12inch action figure at 1/6th scale. There is a wealth of 1/6th scale articulated action figure dolls and equipment mostly in a military vein, ready to place in very large scale vehicles.
Radio controlled aircraft pilots could also be adapted for use in ground vehicles and come in various scales right up to 1/4 but these 1/4 scale pilots can be very expensive.
Most of the figures shown have a specific project they are destined for (currently not the wrestlers). I find a lot of my recent projects are ending up at 1/16th scale. For me it is a comfortable scale to work in, not too small, not too big and it would be cool to have a fleet in a common scale.