Intuitive design and clear instructions can significantly reduce the learning curve
Considering the appeal of Ninjutsu is to play a creature from your hand as an attacker for a surprise strike, it is fitting to have it in a set that has a ninja Planeswalker
Four Imperial Recruiters might be a little slow, it might be better to have more Skyclave Apparitions or other removal spells instead of some of them, and a few other numbers could be tweaked, but I think this is a really good starting point
And thats not all: remove flying counters from your creatures placed on them by Luminous Broodmoth, slow down the aging of Cumulative upkeep cards, like Mystic Remora (or Blizzard, if you feel like putting flying counters on opponents creatures like a monster), allow Undying creatures to continually un-die the (giant robotic manta in the) skys the limit
While the Extra Deck was only comprised of Fusion and Synchro Monsters at the time of the card's original Western release (it was released in 2001 in Japan, when only Fusion Monsters existed in what was then the Fusion Deck), in modern play the card could bring out a whole host of Xyz, Pendulum and Link Monsters with ease -- were it not for the card's errata
