Could you choose the number of PBKDF2 iterations based upon the system time?

I've heard a few people recommend that the number of iterations for PBKDF2 should be doubled every two years (starting with the recommended 1000 iterations in the year 2000 when [PKCS #5](https://www.rfc-editor.org/rfc/rfc2898) was released).

Theoretically at least, you could determine the ideal iterations through an equation based upon the current time. Perhaps something like:

```
year = <current time in years>
exponent = (year - 2000) / 2
iterations = 1000 x (2 ^ exponent)

```

Which would give a value of about 115,196 iterations at the time of writing.

Assuming that:

* The system clock can be trusted.
* The number of iterations is stored with the hash, so that hash verification is still possible.
* Safeguards are in place to stop the system attempting to hash with a ludicrous number of iterations.
* You continue to monitor the actual time taken to hash passwords on your specific hardware.
* You regularly upgrade hardware to keep up with the increasing performance requirements.
* You choose an appropriate underlying hash algorithm.

Would such a system be safe and practical?