Hi,
I agree with you that Coppermine is an absolutely killer application, but I'm not convinced that ecommerce should be built in as part of the package. Two months ago, like you, I thought that it would be a great feature, but now, I think it would be best left as a mod that can be updated, evolved and tested under various situations before being added to the package. And even then, as an optional installation mod.
I suspect that the majority of users don't need ecommerce on their sites. Building it in would make CPG bulkier and possibly slow down the program and increase load unnecessarily for the majority of users. In other words, too many optional settings = too many if..else statements that have to be read before a page is displayed. Instead, streamlining CPG but keeping it readily configurable to accept any number of mods would probably be in the best interest of everyone.
Second, a number of ecommerce mods are already available. Click on the "home" button just above this board and do a search on "ecommerce" will display a number of links to the various options. The author(s) of these mods offer excellent support for their mods and so, for the time being, it's probably best left there.
Dennis