I don't see an issue with that, myself.
Sites like MAL and Anime-Planet (the latter of which I personally prefer, due to its superior ease of use) have that particular niche very well serviced. Duplicating their efforts here, on this forum, to any degree at which it would be comparable in terms of features and functionality, would require a fair deal of time and custom coding... it would very likely also have to be worked on and tweaked every time the forum software is updated. And that's not even taking into consideration the amount of work that would have to be undertaken to create and maintain our own anime database, particularly if we were to try and match those other sites in terms of content - descriptions, screen shots, etc.
My experience is that add-ons of that magnitude to forum software suites like Xenforo and the like tend to be a pain to create, and a nightmare to maintain.
With that said, I'm sure it would be possible to hack something super simple and barebones together, but given that it seems like most folks already have MAL/A-P accounts, I'm not really sure there would be much point in it.
Disclaimer: this is only my personal take on the matter. It's always possible that Optic could pull a rabbit out of his hat at some point and surprise us all. ^^