Quoting your most...questionable (to me) idea.
"4th- The final of the war must be more desperate, something like that Moagim army destroyed the whole Light army and [then] Connacht, Damas and some Herons in last minute kills Moagim Reborn(the made him a trap), Moagim's army collapsed and victory of Light." (Corrected a little by the English teacher in me)
Sorry, but that's more Connacht=Superman than Myth III's story, along with Llancarfan falling and yet him and the gang surviving, which I believe (someone look it up) has "never fallen before [Balor]".
It is an interesting idea for a change, King, but it doesn't really help him being superhumanly heroic...and it makes the ordinary Soldiers seem...well...pathetic.
Part of what's so wonderful about Myth TFL is the Legion's last desperate charge, 2200 hundred men against a quarter of a million, just to buy time to pull of a scheme that might manage to kill Balor. Maybe.
This just has them slaughtered like fish in a barrel against machine guns. Perhaps we can't do the events percisely the same way as far as how they're shown, but it takes a lot of the punch in the story out in the way you described.
Of course, as a note regarding the first to defeat the Myrkridia...
I think, and some other military nut go over this, but I believe the Cath Bruig have pulled back to Llancarfan because they can't hold the other cities now so longer destroyed we don't even know them anymore. So Connacht is the first to defeat them in open battle, in the field...although I still have to wonder why a pack of highlanders from nowhere are able to do better than the soldiers of the finest empire of Myth. Regardless, the Cath Bruig are holding on to Llancarfan and any other heavily fortified cities because the Myrkridia can't really assault them. What are they going to do? Tear down walls that would make Constanipole look like a backwater with their claws?
Someone else will have to tinker out what to do regarding the Trow, I've said my piece for the time being. (I think)
Seraph