Questions and suggested modifications:

Mechanical failure of one engine should have the same effect as shell-induced failure; it should not force the B-17 out of formation unless the prop is not feathered or the B-17 is carrying bombs, and should not require the B-17 to spend two turns in a zone unless the prop is not feathered or a second engine is out. Thus:

Oil pump failure: leak forces the engine to be shut off on the next turn; see Engines Out.

Turbo-supercharger failure: if the B-17 jettisons its bombs (or is already in the target zone and drops them normally at the end of the turn), it may shut off the engine with no supercharger and proceed with one engine out; see Engines Out. If the bomber drops out of formation, this engine is considered to be at half power; it is not considered to be out, but if two engines are at half power, treat as one engine out.

Engine failure: if the engine is restarted at half power, it is not considered to be out. If two engines are at half power, treat as one engine out.

Non-engine suggestions:

Turret failure: The B-17 should not be allowed to abort. (That is, if the B-17 chooses to abort, the mission does not count.)

Bomb release failure: No effect if the bomb bay doors jam before the bomb run, whether before or after the failure. If the B-17 aborts the mission for some other reason and the bomb bay doors are still operational, the release failure takes effect when there is an attempt to jettison the bombs.

Electrical system: If the pilot and copilot are able to control the plane but the engineer is seriously wounded or KIA, the crew may bailout on Table G-6 rather than G-7, or (if in Zone 2) the pilot and copilot may carry the plane one zone further and the pilot may try to land it at -11. On the extra segment, the B-17 is out of formation and cannot take evasive action, but if it was in formation before losing the electrical system, the radio out modifier does not apply.

Once more this is after the General article. Though after rereading my entry, I see it sounds as if any powered turret failure warrants the possibility of an abort. In the original article the Top and Ball turrets were separate events and only the ball turret had this note. I will revise my entry to reflect this. I can see a pilot, in the early stages of the mission, aborting due to a ball turret failure. With the gunner trapped in the turret he would be dead if circumstances required them to bail out. The other two turrets don’t have this worry.

However, the rules for B-17 do not allow an abort if the ball turret mechanism is inoperable due to shell damage. The pilot might choose to abort (and is allowed to abort at any time), but the mission does not count. Therefore, I would expect the same rule to apply if the ball turret jammed due to mechanical problems.

True it is not in the "Original" rules, but it was part of the "official" variant in the General. I would think that if it was in the General Magazine then there is some expectation of being official format, at least for that variant. Since I am utilizing their variant for the basis of my variant, would it not be logical to use it here?

I'm not saying you are wrong, I am justifying its use here. I don't see a historical reason that this wouldn't be a reason for aborting, and a good enough one to still get credit. I'm not sure if the USAAF would count this as a mission or not. In my latest reading there were some questionable aborts that were not punished after the August Schwinefurt mission. I don't know if they were credited, but there was animosity for these aborts.