How long do you think it will be before we see enough cards to build a playable Aegon deck?

I'm thinking that Fiefdoms, Great Pyramid, Temple of the Graces etc. could still be used from standard Targ sets.  Just no Dothraki or Dragons.

It would probably make sense to run Treaty with the South, a Dornish alliance seems to be the smallest stretch of the imagination which would bulk out the card pool.

what essentials would there be to make the deck worthwhile, not just a generic targ/martell alliance?

Just thematically, maybe a Mercenary/Traitor-based deck would work? Or a Baratheon Alliance to represent the foothold in the Stormlands?

Fairweather Followers, Hired Swords, Banner for the Dragon, Disgruntled Mercenary, Maybe Rhaegar for extra flavor. Use Illyrio's Man as a reducer, and Illyrio himself.

For plots, Mad King's Legacy, The Power of Blood, and The Prince That Was Promised would all be thematic.

Of course, I make no promises as to how effective this would be.

 Well the announcement of the new cycle certainly looks like it'll help this along the way - Griff and Young Griff cards sound like an obvious starting place.

Looking forward to this cycle (although it's a ridiculously long way away yet- i've only got 2 packs of the current cycle!