The question concerning whether or not we should/would pay for an expansion restoring this content is a very interesting one.
On the one side, purchasing such a package would essentially mean endorsing the prospect of selling half a game (which already occurs to some degree) - which obviously, objectively is something that many people (quite rightly) have difficulty reconciling.
The unfortunate flip-side to this is that a company such as Obsidian could probably not afford to devote the time & resources required to doing this product if no financial backing were forthcoming (and if no sales were to be made, that backing is far less likely to materialize). This would not only necessitate them working for free, but also assigning a lesser priority to their upcoming projects - which given the current state of the industry, I very much doubt they could do.
A potential, workable (and perhaps favourable) solution to this, would be if they (or someone else) were to be comissioned to create a true expansion pack - with truly original content that has not already been created, whilst simultaneously rendering all the loose ends fully functional again. The question as to whether or not we should buy the expansion pack would be made all the more easy for the simple fact that we were actually investing in new work - not just the remedying of unfinished work. After all, I think that deep-down, most people here would be more than willing to pay the extra money to see this missing content as long as they weren't indirectly supporting shoddy producion methods.