I wish I could add something to this list but I think it's like, Gruul Theft Auto Pod? What is the other idea with the planeswalkers? In what context do we slot it in, Wildfire? I'm curious because there seems to be a lot going on.
You end up with a solid midrange/control monsters deck, with combo and pod sub themes.
Basically,
see the unwritten is a natural gruul card because:
1. Its a great ramp target
2. Gruul triggers ferocious better than other colors
3. You are more likely to get sweet monsters off of the top 8 than other colors
You can run some TOL tutors to help set it up (beast tracker/worldly tutor)
There are also a few other big cheats cards that you could run:
1. Garruk, caller of beasts
2. summoning trap
And there are a lot of tutor effects you can run with them: besides the aforementioned tutors, you have
primal command,
summoner's pact,
fauna shaman,
survival of the fittest.
The planeswalkers provide the value train and are the glue that hold the deck together. While card draw options in green suck, planeswalkers can just sit there giving you a tempo positive effect every turn, which is a big deal when most of the deck will probably cost 3-5 mana. It lets you sequence multiple effects in a turn if you can stick one.
The ramp options are stuff like
abundant growth (cantrips, 1 mana),
harrow (risky/powerful), and
sakura-tribe elder (fogs a turn, ramps).
Vines/blessing help keep the deck from folding to bounce spells.
Than you have fatties you want to cheat into play. I went a little outside of the box with Thromok (which is sadly too cute for titan land) but its a sweet thought having him come out, eat a bunch of red goblin tokens, and than swinging for leathal off of a
reckless charge. Take your pick here for fatties/big midrange guys:
primeval titan,
craterhoof behemoth, whatever.
Than you have a bunch of flexible haste effects, and if you are going to be running a bunch of threatens anyways, you might as well support G/R pod. Another very strong archetype in its own right.
After that you have some mass removal options to help you stabalize, which won't kill your wall of fat. Mizzium mortars, anger, and firespout are the most interesting, especially since firespout naturally pushes people into gruul.
Wildfire dosen't fit into the deck because I don't think its a very good card.