The Dremel 4000 (variable speed) kit with Flex Shaft accessory is the way to go. Make sure you get some extra fiber reinforced cut-off wheels too - they are probably my most used accessory.

I'm currently on my 5th one (in 35 years) because I only get 4 - 5 years out of them because I have used them for jobs larger and more heavy duty than they were intended for. Since I now have a "big boy" industrial air compressor and can now actually really use my air tools including my 1/4" Die Grinder with bigger scale tools for those large jobs and leave the Dremel for the delicate stuff.

Don't make the same mistake I have!!! If you find yourself using your Dremel often, when it fails from over use get yourself a Foredom Tool! They are WAY stronger, have much higher quality shafts, tools, and will last a lifetime. They are the professional ones the jeweler's use. Yes, they cost $300 -400 bucks with a few handles but you will not be buying new Dremels every few years and they are so much more powerful you can safely use 1/4" burrs and wheels in them. The next time my Dremel goes, I am getting a Foredom SR!