A wallet that tracks your fiat cost base is important to develop so that U.S. people can pay taxes, but "discussion" about it among people who don't have the capability to make it (not to say it is difficult because it is a standard requirement for enterprise accounting since 1800s) is moot.
Did you not read the link I gave you upthread on that?
The issue is not just record keeping and calculation, but also planning and timing. The timing on planning interferes with the timing-fungibility of money. This is one of the reasons why investments are not money.
Here is the link again for you to read my short explanation:
https://bitcointalk.org/index.php?topic=455141.msg5953000#msg5953000