I totally disagree Elk
In this deck, we have no vehicle synergies, and most of the creatures we'd tap are actually higher power than the vehicles. This is a ground game deck, and it's actually big enough, and fast enough to give vehicles decks pause. Putting vehicles in would actually slow it down - assuming this deck is viable at all. If not, then vehicles would be better in Rakdos as before (or the more popular Mardu). In other words, play vehicles in the vehicle colors, imo.
Other note: insult // injury looks good to me too (maybe better than my 3/3 idea, tbh), and it should 100% work with fling.
I don't think the vehicle synergy needs to be high for it to be effective. The value of the individual vehicles themselves are typically strong enough without having pilots/synergies that benefit. The power level is fairly on par too. The majority of cards I've listed are 3 or 4 power which is similar to the vehicle options.
The problems I have (and why I was saying it needs testing) is what I think you're saying too, the potential tempo loss and the new meta. The deck might be fine just putting out more beaters and swinging instead of dropping a vehicle (especially if the opponent blows you out with removal/bounce/flash etc). The meta also could shift to control which would make vehicles worse (again due to tempo as well as speed). We didn't get all the artifact hate though (which I assumed we would) so that's something to consider.
Fleetwheel Cruiser might still be a good option though. A haste/trample beatstick (similar to the
Glorybringer consideration) might be worth testing. Same for the Skyship which is a win condition in it's own right. I still haven't figured out how high this curve should go (cause I want to jam
Chandra, Flamecaller in) and what goldfish turns we should be expecting.
Right now I'm stuck on the removal/interaction suite. There are a couple red considerations but they're just out classed by several other colors. It's part of why I was thinking the vehicle/artifact support to make a 3rd color like
better. I still want to see how the deck does with
Insult // Injury and possibly
Fling (or any other red burn that can go to the face). I just wish Insult wasn't rare. Still, the deck might not need much interaction to get it's wins and could be played with the idea that the opponent has to answer.
As I was listing in my brainstorming above, these are all options to test in this particular deck to round it out and I'm sure it'll get modified as the meta clears up. I'm definitely looking forward to testing this list though (and totally resent TIMH for posting a similar list up first!!).
elk