I don't think this is necessary.
In addition to Jeff's explanation that this is trickier than opening salutations, what % of first posts (or any queue really) do you suspect have only the problem of TIA? In other words, if the post is going to be edited for other reasons anyway, what does automating buy us? And if it really is the only problem with the post, is it worth editing (manually or automatically)?
The opening hi and all that stuff gets in the way of getting to the point. An ending thanks after making the point is really just not as much of a problem IMHO. In fact it's nice to see that not every bit of cordiality and courtesy has been automated away. When I'm editing a question I remove it but I won't edit a question just to remove it.