Felix said:
And ...To which you've not rebutted. If it's so weak, then by all means: topple it. Which particular premise do you take exception to? ...
Your whole argument comes from the wrong perspective. The normal rule is that you get to select spells from your class spell list - Sorceror description notwithstanding.
This places the burden of proof of selecting ANY spell (regardless of class list) using "Extra Spell" to be squarely upon the shoulders of those who would like the rules to allow that. This burden has not yet been overcome.
Simple as that, really. There is no permise to argue against, really, - it is you who must explain how the normal rule has been
specifically changed by this feat - especially in light of the very different and specific wording in the otherwise virtually identical psionic feat. I have not yet seen any such explanation.
So, to this point, I see any reading of "Extra Spell" to allow a selection form another class' spell list to be, at best, an extremely odd and incorrect hyper-technical reading of the rules.
In other words, I think you are just fooling yourself to think that your reading is really a legitimate reading of the rules.
That said, the rules are really just a starting point for any game, and any DM is free to interpret the rules in any way at all - including ways that the vast majority (about 90% if the poll is to be believed) of us would not do so.
So..., here's the deal:
1. The overwhelming majority of us would not allow your reading.
2. The "official" ruling (FAQ) is that only class spell lists are allowed, as normal.
3. If you can convince your DM, more power to you... and that's all that really matter in the end, right?
However, if you intend to the arguments in this thread to convince your DM, I think you will fail.