This is how I'd book Angle for the next year or two.
Have him announce his intention to retire from the sport of professional wrestling soon, but not give a timeline as to when he is going to go out. But do have him state his intention to win the title one last time. Once the Roode/Storm thing reaches its conclusion, Angle will be the next to win the title.
At this point he would announce that now that he has won the title for the final time, he is going to retire. As soon as someone can beat him for the belt.
Have him go through everyone, and I mean everyone, coming closer and closer to losing each time, sort of like the Undertaker and his streak, making each competiter look really good, but still having him come out on top due to his sheer resilience and knowhow.
Finally, after a year or 18 months (yes I think he needs to hold the belt for this long for the story to truely work), whichever young wrestler is really over and they want to push to the top, can take the title off him and have the bragging rights of the man who retired the legendary Kurt Angle and took his belt in the process.
Some people wouldnt like the idea of keeping the belt on someone for that long, especially an ex-wwe veteran like Angle, but imagine the meaning behind it when he finally loses it. The people he defeats in the process will all gain something as they will have taken angle to the very limit, the person who finally wins it will become a megastar (by tna standards) and the belt itself will gain such a boost in image and meaningfulness.
Now, with regards to Angles actual personality or "gimmick" through all this, it would work as him being a heroic face or a cocky heel, but I'd personally perfer him as a face like Taker.
Thoughts?
(First post, so dont be too harsh

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