ones thing that could be added to the time element is depending on experience and or if you have beat the game before or how many cars or engine installs you've done certain tasks and can less time as you "level up" or gain experience.
What if the experience was for one model in particular, and leaked over to similar work on other cars?
Example: I buy a rustbucket of a '75 Camaro and replace the engine. Replacing the engine gives me 100 XP for '75 Camaro engine replacements and 75 XP for engine replacements.
Alternatively, what if the XP gained from one job carries over more or less directly to jobs that are similar, and less so for jobs that aren't similar?
Example: I buy a muscle car with a bad transmission. Replacing the transmission gives me 100 XP for transmission replacements, 75 XP for drivetrain work, and 50 XP for exhaust work and engine replacement?
except the engine a 75 camaro is very common and would spill over to many other models of cars. we could pretty creative with this. if i were to "draw the line" and believe me i suck at drawing. i would do it by make, like FORD, chevy and mopar and split that down to i6 and v8. you do one mopar i6 and you get xp for all mopar i6s and some for xp for chevy and ford i6s. or even simpler just v8 and i6 regardless of brand. for certain years or rather decades things were pretty simple like 40s and 50s cars once you had done a few you pretty much knew 'em all regardless of brand.
fuel line, throttle cable, transmission/bell housing, engine mounts, radiator, alternator and headers.
bit, of blanket statement but, i like to keep in mind there is work in evolved for everything that will implemented in the game. but, anyways this is probably one of the most though provoking threads i've seen in a while.