So, I'll go into my initial thoughts on the QA role...
We (Jmo and I, as we both set up the game even though I ended up doing the GMing) wanted to vary the game a little from the previous one, but since neither of us were veterans of the game we didn't want to change it too much, as we did not know how many of each we would need to balance it.
Jmo came up with the mole and QA roles. Initially, the QA could ask (iirc) 3 yes/no questions, one per night, and they would be answered by the GM in the thread. His questions also did not counter the mole or the copscan immune SK. The idea behind this was we brought in a new role for the town (QA) and a counter for the mafia (Mole).
We decided this was way too overpowered, so we set about lowering the power of the QA. We made his ability a one-shot one, and at the same time, I came up with the idea that instead of the mole being a counter to the QA, the QA should be a counter to the mole, otherwise the role is too similar to that of the cop. I'm still not sure if this was the best idea, but it seemed so at the time so we made the QA's question bypass scan immunities.
With the scan immunity bypass, though, the QA was overpowered again. At the time, I had not thought of the type of questions that came up in this thread (I was thinking he would ask things like is there a mafia member among X, Y, Z) but I was aware people may find a very good question that I had not thought of. I tried to come up with a way to make the QA's role more interesting to play while at the same time reducing his power.
The idea of the question being answered on his death seemed great, as it adds a completely new dynamic to the role. The QA's question is much, much more powerful if asked late game (While you can make questions that stay relevant towards the end game when asked at the start, the question can become a lot more direct and foolproof when asked when there are less people around), so the QA wants to survive the early game. However, the town can't afford to waste a lynch on him in the late game, so he needs to get the mafia or the SK to kill him, which they won't do if they know he's the QA. Therefore, he needs to survive to the end game without revealing his role, and then make himself a target for the mafia/SK and get himself night killed.
Of course, all of this depends on the QA's aim being to die. The QA using his role to make sure he wouldn't die had not occurred to me - I figured that if he was going to be lynched at any point he would go with it, as it benefits the town, or if he didn't want to die yet he would roleclaim and then ask the town to lynch him at a later time. The QA becoming an invincible townie was not what I had in mind when making the role, and I think it defeats the point of the role - roles are supposed to make the game more interesting, but this just allows one person to sit out of the game with no fear of dying to lynch or kill.
If there was some way to make dying much more preferable to becoming an invincible town player to the QA, without making his power overpowered, then I think the role would be great and build on the game. However, in its current state it's a destructive role to the game rather than a constructive one, so I don't think it should be used in future games.