Adding DLC weapons and more or less anything that affects gameplay (especially online interaction) is a disservice to the versatility that the prior souls games established as a staple of the series. The Artorias DLC was so widely anticipated and desired that the additions they made were justified - many had been playing for a long time, and additions were welcomed at that point. They were new variables to add to an extensively 'solved' equation.
Day one (or even early on) DLC's change the tone from 'additional content' to 'exclusive content'. While some may consider this a semantic difference, I think this is exactly why many are so upset (myself included) over the possibility of this preorder and launch content. It stops being a reward for dedication, and starts being a reward for giving them more money.