I go with agree team again Fairy Tail 290 I agree with the second, third, and fourth point.
That mysterious man is probably won’t be revealed yet next chapter and Jellal will probably lose sight of him.
Since Lahar is already there and I presumed that he heard what Doranbalt say about Jellal is not Mystogan thing, Doranbalt’s lies must be so believable to convince Lahar which is hard to happen seeing how strict he is. Lahar is having role in the anime, so my opinion here might change a bit.
I want new spell from Jellal, Lahar, and Doranbalt greatly. Maybe Ultear and Meredy will come to help, but that will pretty much confirmed that Mystogan there is Jellal.