I think you are looking at the idea on the wrong end.
First off, it's not so that we can have two Awakening reps instead of one. I genuinely think it offers a more engaging gameplay prospect than both Chrom or Robin. Secondly, I would say it does represent something important in Fire Emblem. Unity, comradery, and most importantly Support. Yes, there are technical difficulties, but now that I have assessed what Mr. Sakurai was having a problem with, I can still say it's doable.
The reason why I support Chrobin is because it's an opportunity to pull out a combat system commonplace in many of the popular fighters these days: assists. The benefit of an assist system is of course the fact you can call in an assist while you are otherwise occupied. It's a combo system, through and through, and I would LOVE to see it in Smash Bros.
It would be handled in a simple fashion:
- The supporting character stands ever so slightly in the background, and cannot be attacked while not in use
- The supporting character is "blackened" out while they follow the active character, and they run at 30 FPS on the 3DS
- Neutral, side, and down specials cause the supporting character to emerge from their blackened state to attack
- Supporting character only has to check for collision with the ground beneath their feet to reduce CPU load
- Supporting character cannot leave the stage, and only work while the active fighter is on/over the stage
- As long as you are not in hit-stun, you can call on the supporting character, and can work even while you are attacking/grabbing
- If a supporting character is attacked while they are being called in, it's simply cancelled and you incur a delay before they can be used