Hey, with mta vc 0.3, i think it would be a good idea if you could choose to enable the CRC check (the thing that checks 4 modified handling and etc) when you start the server. thatway, if u are on a lan with ur mates, u can still play with modded handling.
or alternativley, i am currently writing a GTA file backer uperer in VB which backs up ur Vital files, then u can make it automatically place the original or modded ones in ur VC dir and start VC. it has presets for MTA and a full backup and takes less than 2 secs for jutst MTA files
This way u can have modded cars in SP, then click one button, and ur game works perfect in MTA (all cars are restored)
Let me know wat u think!
(the backer uperer will be on my site soon)