That is correct. It'd be awesome if someone here customizes their larger scaled models, because I ordered two Bburagos to do just that. I'm all 1:64 scale otherwise.
I have customized quite a few of my 1/18's. Anything from just lowering all the way to wheel swaps and engine swaps. Normally just detail painting though on a lot of cheaper models. Here are some examples of my modded models:
Highway 61 Dodge Challenger T/A "Ultra Challenger":
Engine swap (Hemi 426)
Wheel swap
Added carbon brake disks and calipers
Painted all chorme matte black or gloss black
Added front spoiler
Moved battery to the trunk
Seat swap (GMP racing buckets)
Steering wheel swap (GMP race wheel)
Added fire extenguisher
Replaced exhaust pipes (due to engine swap)
Lowered
AUTOart Skyline R34 GT-R:
Lowered
Wheel Swap
Metal brake disks
Welly Camaro SS:
Lowered
Wheel swap
New brake disks and calipers
Motor Max Chrysler ME412:
Wheel swap
Repainted brake disks
Painted headlight housings black
Added side windows
Painted tail light housings black
AUTOart Panoz Esperante GTR-1:
Wheel swap
Painted various bits black
Removed lower headlights
Added front and rear tow hooks
Added spark plug wires
Repainted some other engine bay wires
Repainted brake disks black to simulate carbon
Raised car slightly (stock it was nearly as low as the race one)
Bburago Ferrari F50:
Added seat belts
Added brake disks and calipers
Painted headlight housings black
Added small front side windows
Minor engine detailing (mostly painting)
Repainted various bits around the car