See Requests for Aid.

Suggestions for commons:

Sorcery, , "For each player, you may have that player shuffle his or her library." / "Any number of target players shuffle their libraries." Or add to make it cantrip.
Reasoning: Works to mix in any Sift cards that have been put on the bottom.
Complication: Does rather want the same slot as Restock though.

Aura, , "Enchanted creature blocks each turn if able."
Reasoning: You want a green "negative Aura", and there are very few such effects, as I discovered when doing some research for Geass :)
Complication: You already have Sense of Responsibility which is far too similar.

Creature, , 3/3, ": Target land becomes the basic land type of your choice UEOT."
Reasoning: We discussed Dream Thrush over on Suggestions, but obviously a Sea Snidd would be better in green, especially looking at your skeleton slots. Could be 3/4, or 2/3 .

Instant, , "Add to your mana pool. Prepare ".
Reasoning: Seething Song seems an exciting candidate for a Prepare spell, and it interacts nicely with the firebreathing and Stonecourser. You could add another firebreather at common or uncommon.

Wonderful suggestions, Alex! I'd totally forgotten about my own Suggestions page.

You're right that a "negative" green Aura is very difficult. Maybe I'll shift Sense of Responsibility into green and come up with something else for white.

I'm particularly in love with the suggestion of a Seething Song variant. How did I not think of that? It goes nicely with both Wandering Minstrels and Stonecourser.