...because I'm bored, I'll do a little brainstorming.
How much capital do I have? What's my target demographic? Who should I view as my competitors?
Assuming I have unlimited capital...
First and foremost, I buy up every license I have to until I'm the SOLE copyright owner to the Commodore/CBM name. With unlimited capital, this means I'd be buying all of the various 'Amiga' names, too, and also probably Cloanto.
It almost seems that the current owner somehow thinks that Apple, HP, Dell, Lenova, etc. are who he's up against. I think that, to a SMALL extent, Apple might be, but certainly not HP, Dell, Lenova, etc.
The C64 is, in my mind, an oddity in that it not only competed against Apple (and IBM) back in the day, but also against Atari, Nintendo, and Sega. That is to say, it's a computer, sure, but it's primarily an entertainment computer. (Okay, I guess that was true of all computers of the era to some extent, but in my mind, the C64 was better at it than other computers...)
I'd say that our new C64 should largely be designed to be used on a television, in the living room, rather than in the study. Towards that end, I really see Sony, Nintendo, and Microsoft as my three largest competitors. I'm not saying the new Commodore should be designed as a console, but rather that it's chief competition for the time and money of a perspective buyer are these other consoles, and that should garner some serious consideration when the feature set is planned. Wireless HDMI, high-def video playing capability, and wireless internet access would probably be must-haves.
I'd say that our new C64 should also be designed to be SIMPLE. The OS should include a modern browser, a capable email client, and a word processor capable of loading and saving office compatible documents. Creating a Commodore version of iLife would be a good idea, because initially the amount of software for this beast is going to be limited, so why not give the consumer what they need out of the box. I'd say that if you could include 10 revamped versions of iconic C64 games that'd be perfect. I'd also borrow heavily from Apple/nintendo/microsoft and have a Commodore version of iTunes/Wiistore/Xbox Arcade where you could, for a small fee (a dollar or two a game?) download classic C64 games in some sort of encapsulated format that includes the documentation in a PDF format and a simple click-to-play format. No fooling around with setting up emulators. Every game you buy comes ready to play without your having to fool around with anything. In addition to repackaged classic games running in emulators, you'd also want to give developers the opportunity to sell 'modern' games designed to take advantage of the hardware.
The more I think about it (again, pretending that capital is no problem), the more I REALLY like the idea of using BEOS as the core of my operating system and having Windows-support available as a 'boot camp' sort of option. I'd also pull an Apple and work hard to keep my OS off of other hardware. 99.9% of the reason to buy Apple hardware is the desire to run Apple software. I'd say the goal with our Commodore OS should be the same.
The aesthetics of our C64 should be a nice, simple homage to the original breadbox. I'd hire the best design team I could find and give them pictures of the original breadbox, with instructions to 'modernize and pay homage'. There should be 0% doubt that the finished product is the 2010 version of the C64, and there's a lot more to that than just being a keyboard with a system board integrated.
I think I'd dub the system the Commodore 1024. Give it a medium powered Atom and a gig of memory. In 6 months, we'll launch the Commodore 2048d, which is a desktop system with wireless mouse/keyboard, a more powerful Atom, 2 Gigs of memory, and an available matching 24" 1080p LCD panel. 
Don't even get me started on a year or two down the road, when we start taking advantage of those Amiga trademarks we bought up today. 
You expect to compete on equal terms with a $150 Xbox360 for gaming/home entertainment using an Intel Atom based solution? Don't think you've thought this out well
Doesn't have to be a C64 specific successor, it's only now that Commodore and Amiga are two distinct brands.
IF, and I do say if, there was ever to be a machine which is a spiritual successor to the Amiga/C64 again you would need something pretty special. It would need to be priced half way between an Xbox 360 and a PC capable of running DX10 games like Alan Wake at 50-60FPS, so that would be approx $800 minimum. It would need to cost half way between the two....so about $300-400.
And then....you would have to do something innovative with the OS and applications. In 1985-87 on an A1000 you could digitise photo-realistic images, sample sounds for instruments in music, create cartoon animations or photo montages etc all using the best ideas like a GUI desktop with multi-tasking. Also unlike PCs it was a simple case of popping in your game disk and playing a game fuss free like a console (after loading KS once with on screen graphical prompt).
What could you do with your 1984 Mac 128k? Nothing much beyond playing with the GUI OS really. And your DOS/Windows v1/v2 8086 PC? Bugger all except boring office stuff and some rubbish CGA ports of classic arcade games like Zaxxon or text adventures from Infocom.
Anyway OS X/Linux/Windows (any) can happily do anything 99% of the Facebook/MSN generation today want to do. OK some do it faster/more reliably than others but the difference is unless you really put in 25 years of OS advancement since the GEM/Mac/Amiga time of 1985 like things bordering on artificial intelligence built into the OS you can't claim your OS is doing something other machines can't. And that's the difference today.
And Microsoft/Sony will not licence their console motherboards for you to write an OS and sell as a rebranded machine and there is no way to build a PC with that sort of power and features within the $150-200 gross cost.
So you are basically screwed on the hardware price/performance AND the OS. That's why today we are back to the pre C64 days of expensive gaming rigs and functionally competent consoles for a fraction of the cost of high end computers but sod all computer like functionality and freedom. There is no best of both worlds type hybrid for less than equivalent PC/Mac.
Atom CPUd low end stuff is paired with a purchase of an xbox 360 to meet gamers needs. So they can play stunning games and watch 1080p media but still also blog on Facebook/surf the web/chat on MSN etc.
