I
do get where this chap's coming from when it comes to not wanting to be too "meta-game," as the same desire holds true for me as well. See, what makes pokemon decks so difficult to structure is the rigidity of the card-count (no more and no less than sixty). Thus, when it becomes expected to
always have certain cards, it leaves little room for individual players' creativity. Claydol is a no-brainer (same for uxie) but when the game begins dictating which non-supporting cards a player must have for the game, it tends to get repetitive.
That being said, if you plan on using flygon at all, you might as well make use of its natural abilities. You have two attacks you can capitalize on. Most players use power-swing; and why not? if you play Claydol, it doesn't take much strategy to pull off a power-swing swarm/assault, and it makes building the deck pretty flexible. Flygon is a card that allows for a great deal of personal choice when it comes to supporting cards for two reasons: (a) the flexibility of power-swing and (b) the colorless energy type.
So, if I were to evaluate the usage of Leafeon and Flygon together, I would have to say that the strategy, while effective in separate tones, does little to provide collective support. Leafeon's energy forcing allows extra energy attachment, but Flygon's attacks aren't variable in terms of cost (power swing will always cost exactly 3 and provides no benefit for any more than that). Leafeon
is a valid card to use as gunpowder for power-swing; but, it isn't your only option.
Now, as for suggestions on what might assist your strategy, I really have little to offer, unfortunately. There are a great many cards that function perfectly well with Flygon (once again, because Flygon is so sickeningly versatile) so any choice isn't really going to
hurt your strategy. However, the trick here is finding that perfect team that will
help your strategy.
Now, I do have one suggestion that might aid your strategy. Take advantage of Flygon's "rainbow float" body by including pokemon that could
benefit from free retreat cost. Remember- you can use whatever kind of energy you want, so if you were to say, run heavy pokemon, you would gain that advantage.
Happy deck building