Since wands by nature are limited to 4th level spells, I think introducing epic feats to allow wands of higher levels might be overpowered.
You should note that that it takes Divine Rank 6 to create wands that exceed the normal limits for such items. See Craft Artifact salient ability. While not everyone uses the rules from Deities and Demigods, you should at least take them into consideration or mention this information.
It also takes ML 17 for a psion to craft a 9th level dorje.
Wands themselves are already rather underpowered, and by the time you get to epic level, there are a lot more overpowered things than being able to shoot a certain spell at minimum caster level 50 times for a huge chunk of money.