Credits to TensaiOni's website and COH2.ORG's recently published veterancy guide.
Here's the spreadsheet:
https://docs.google.com/spreadsheets/d/1kzY9-UwZSQ19_EL3LTZoBHjMCwD1ZaDrEtedjKap4wM/edit#gid=110608506
Generic stats are in grey, 'offensive' stats in red, 'defensive' in green, and others in blue. Miscellaneous stuff like Command Panther aura and vet 1 abilities are right at the end. Every time a veterancy bonus affects the unit, the particular statistic is shaded in darker.
Example:
For example, the Puma has a 33% damage buff applied once at vet 3, hence the moderate shade of red. The M4C has two reload buffs of -20% and -30% reload time at vet 2 and 3 respectively, hence the dark red.
Disclaimer- I don't know how exactly the cooldown/reload/aimtime works for flak vehicles with multiple shots per reload- the numbers for those are timed directly from the game, and are approximations.
Armored cars, halftracks, and artillery will probably come later- machinegun weapons don't fit on this table nicely.
Lastly, do please point out any mistakes if you spot them, and i'll rectify the errors whenever I can.