The argument, as I read it, is that (1) we're trying to get younger on defense; (2) we're trying to shift some of the salary cap investment from the defense to the offense; and (3) we're rebuilding, so why would we need to get a pro-bowl corner anyway. Signing Ty Law does not support any of these points, unless under certain circumstances.
Poole is likely lost for the season. He's got a minimum of 4-6 months rehab (based on medical recommendations on this type of injury), and there would definitely be questions on how effective he could be afterwards. This would open the door for a one-year "stop-gap" solution and may force us to stray somewhat from the "get younger" argument.
The only way that I think we would sign Ty Law is if it's a short term, low money contract -- like a one year, at or near minimum contract. I don't ever see Law signing this kind of deal, and thus, I doubt very seriously that Law will be coming to Miami. But, if for some strange reason, Law would sign such a deal, then the salary cap impact would be minimal and thus could still allow for money to shift to the offensive side of the ball.
I also don't believe too much in that we're rebuilding. I still believe that we have a lot of talent, we just need someone to focus that talent in a positive way. I think Saban and the coaching staff are definitely capable of doing that as opposed to our previous staff. I honestly believe that if this can be done, we could at least double our wins from last season.
So, all in all, I only support a Ty Law signing if it's a short term, low dollar contract. Because if this isn't the case, then yes, it violates the very valid points in the argument. I also think that there's no way that Law would go for this kind of deal. So, it's a mute point.