You don't really have to build anything if you don't want to...
Diamond select recently did plastic 1/15 versions of the part 1 and part 2 (mechanized hover wheels) that include lights and sound effects. Both have opening doors. Good toys, but they are toy quality.
Sun Star did some great metal versions a few years ago in 1/18. In addition to stock deloreans, they did mulitple time machine versions also. Very nice metal-models... all factory built/painted with opening doors, hood and engine cover.
Welly had released 1/24 diecast time machines. Three versions IIRC, all with opening doors... which you usually don't see at this scale.
Want to build a kit? Aoshima is the only way to go. Again a working hover mechanism to make the wheels turn in.... comes with every kit. They make all 4 versions, and as mentioned the new releases include figures to go with. The older releases do not have the driver, and can be found in AMT boxes also.
The Polar lights is a fun snap kit... and its the only one to boast a chromed body. TBH, at this scale you don't want a chrome delorean... it doesn't look right. The detailing leaves much to be desired, if you've already built an Aoshima version.
No need to modify a stock delorean with all of this out here already. Very recently mattel aquired the rights to Universal's BTTF merchandise. Mattel's own Hotwheels had been making stock deloreans all year... and I'd imagine we'll be seeing a lot of new products soon.
