In the Journal, if you give the Trumpet to the Arbiter and not help either of the Kingdoms you can end up an independent kingdom (see posts by omgzed earlier in the thread )

I have played this game enough times to have given it to everyone and noone, and I can confirm that it has literally zero impact on the game regardless of what you do or don't do with the trumpet.

This is very typical of the entire main story in MM7.

The only real difference is in how much experience and gold you get from this whole quest line.

I see what you mean: the three quests to do with the war (human queen's, elf king's and the trumpet one) are essentially side quests. The seven dwarfs being once rescued, the next main story-line quest is the one to choose Light or Dark for the new Arbiter. By pausing the main story for 4 months (minimum) the war gives us time to finish our early promotions.

Even the reputation gained in the royal palaces seems to stay there and not make any difference to the shop-keepers outside.

I think 3DO had grand plans for MM7 and then rushed the game out the door instead of making the game truly epic.

The segment when the true identity of the advisors is revealed is the shallowest plot twist in any MM-game I've played (MM6 up to and including MM9).

Like I said, I'm very sure that they had very different plans for the main quest at some point.

I totally feel the same. I only found out about it about a decade after playing the game, since I never played MM6, and felt they totally wasted this reference.