Redoing old Projects. Asking for trouble?

@Aaron Mustamaa.... is wondering if and when it's a bad idea to redo old ugly projects.

Scenario

A dead-weight project for a big brand that took 2 months out of my life is hanging in limbo between worlds: the world of ugly work done just for money, and the world of actual quality reel work, waiting anxiously for its boatride back across the Styx into the shining world of portfolio pieces.

I hate thinking of all those months gone to waste just to keep my lights on, and I can't just let it sink into the junkpile of history, so I'm redoing it in my own image, with the bells and whistles I originally put in the boards. Doing this, however, raises some concerns.

Concern #1

The obvious grey area of copyright. If the client owns the copyright, you're infringing on your own work by making a derivative work of the project you delivered to them, and may also be infringing on additional usages of their logo if it is included in the remake.

In the real world, I am 98% confident that said client, and most others in this hypothetical situation could not care less, unless you're somehow affecting their brand or tarnishing their image or that sort of junk.

Concern #2

Waste of time? This is for a portfolio anyway, so why not put myself in the shoes of a producer running his eyes over my portfolio. Upon seeing this good-looking but reworked project, what's stopping him from taking one look at it and saying, "well if you couldn't muscle your creativity into it the first time for the client within the time and budget, how are you going to do it if I hire you on my project?" A very good question.

Conclusion. It's a big brand, and there is decent work in the spot, just not great work. If it had just a little bit more polish, it would shine like no other. i just hate thinking of all those months gone to waste just to keep my lights on.

Thoughts? Experience in this situation? Comments welcomed.