I don't know what could be done with a stock meta - the advantages of the modded meta are too great for me to consider returning back to it. Here is a list of the cars which I have found work well with their respective modded cars:
Crown Victoria - STANIER (police also works but Stanier feels more like a Vic)
Taurus - FQ2
Explorer - GRESLEY
Charger - This one is weird. Two different 2015 models behave entirely different from eachother - POLICESCO's work well with FBI while Bugs' doesn't. POLICE2 works well with some models - BUFFALO and BUFFALO2 also work sort of well but all seem to have a form of the inverse tracking issue, especially pronounced on 2014 models. Experimentation is needed here
Tahoe - BALLER, BALLER2, GRESLEY - Tahoes have issues with rear-end-squat and easy spin-out that is more pronounced with certain handling lines. Experiment with large SUV lines to find one that works the best
This pretty much covers everything - if there are new vehicles or ones that don't work well, finding the vanilla equivalent and using its handling line in the vehicles.meta entry (as long as it has the same number of doors) will work well.