I'm more curious about how certain mechanics will translate into the Warriors setting, if at all.
For instance, there is usually some form of leveling up and some form of acquiring weapons and strengthening those weapons. The details vary by installment, as expected from a franchise willing to experiment. . .
[spoiler=For instance]
In Dynasty Warriors Gundam 3 your pilot leveled up through acquiring "pilot points", but pilots themselves could only affect 3 stats and an extra bit of data - namely, pilots had the Melee(Damage), Shot(Damage for ranged attacks), and Mobility (base movement speed) stats, and they were either Normal, Cyber-Newtype, or Newtype, which determined the use of mobile suits.
The actual mobile suit determined the base level of all stats - Melee, Shot, Durability(hp), Armor(Defense), Mobility, and Thrust(Length of the boost gauge) and determined the fighter's move set. By destroying enemies you would acquire ranked "plans" to build a mobile suit, with more expensive plans providing higher base stats and more customization slots to increase those stats. Mobile suits could be outfitted with a certain number of these stat boost determined on construction, and even plans of the same rank had different custom slots and stats. To further the customization, every mobile suit had 3 slots for "Special Equipment" which could be as simple as increasing the damage of a specific attack during a combo to drawing enemies towards you when you attack and recovering a percentage of the damage you Deal. Many Rank 1 (Read:Protagonist/Antagonist/Super Prototype/Important mobile suits) suits also had an unlockable fourth special equipment (which was always set once unlocked) which conferred a significant bonus for the rest of the battle after getting 100 kills in the field.
In Fire Emblem, you have leveling, reaching a class rank for a boost (possibly a choice between two classes for variety), and then leveling again. A simple system like this could be used in a myriad of ways - it could be a simple as "Reach this level and you'll get a stat boost and a new combo" or it could be a determining factor in a units moveset, stats, and equipment. Characters could have fixed promotions or they could have more open ended, Gaiden/SacredStones/Awakening style promoting. Classes could be out the window altogether, or they could be another part of a character's stats and abilities. Where they GO with classes is entirely up to the dev team, of course, and there's a good possibility that they will look at it from the Warrior's point of view rather than the Fire Emblem point of view, which could change the outcome by quite a bit.
As far as scenarios are concerned, one part of the game I have always found challenging and rewarding is playing a stage where the historical events of a battle can be averted when the player comes back much stronger. Chapter five of Genealogy of the Holy War sounds like a prime example of such a scenario - buy a good mount and intercept the entire enemy Wyvern force - and still have time for tea and keeping Sigurd's army together (because someone will have inevitably have gone off to lead the attack, and thus require saving. Again.)
And I feel as though I'm running on a bit long here, so I'll end it off here.