If you want to abuse Misthollow Griffin I will definitely try out Commandeer. Another card that comes to mind is Serum Powder. Nevertheless, I still don't think one can gain much value of these synergies.
First, what I'm terribly missing is any creature with double strike, the most useful ability Wanderer can get. What is bit unpleasant is the fact, that the best things that come to mind are not in your colors (not very surprisingly) - Mirran Crusader and Warren Instigator, which would help you get Wanderer out.
Second, you could abuse more the changeling ability, e.g. a copy of Haakon, Stromgald Scourge for a bit of persistance, especially when combined with Mirran (or even Phyrexian) crusader. Seems like you have a bunch of ways to put him to his beloved grave... I guess there are plenty of cards that will abuse the tribal topic - e.g. Swarmyard,...
Third - is there any chance of beating combo? You should squeeze at least any discard (Inquisition of Kozilek etc.).
I like this idea very much and I've been thinking about it for a while. If budget is not an issue, than addition of white might not be a bad idea - Noble Hierarch becomes even more useful (and is better than BoP for Constable anyway), Angelic Destiny on turn 3 might end the game pretty well. One can even mess with Geist of Saint Traft.
In your colours, Cold-Eyed Selkie will benefit from same effects as constable ;-).
Nice deck ;-).
The suggestion of Geists is kinda obvious. Another option for 3CMC beater could be Mirran Crusader, or at least in the sideboard. Unfortunatelly he's vulnerable to Path to Exile and Lightning Bolt. On the contrary he's Abrupt Decay and Dismember-proof ... and double strike counts.
Besides that a few enchantments come to mind (though less aggroish, perhaps as a sideboard agins tron and such) - Sea's Claim, Convincing Mirage, Spreading Seas...
In the last version you posted probably Giant Growth. Good progress with the creature base... Only other creature that came to my mind was Kiln Fiend...
Further, Gitaxian Probe is not bad in this kind of deck.
PS: You'd better replace Unsummon with Vapor Snag.
I played a little BUG tempo with Quirion Dryad etc. before the release of RtR and was wondering about potential abuse of new izzetian cards in such deck. There id definetely a card worth consideration - Ground Rift - which can help your big creatures lacking evasion get through, provides good fodder for your Nivmagus Elemental and might be quite hillarious with Wild Defiance (sorcery Giant Growth with storm counts).
Second, you could abuse more the changeling ability, e.g. a copy of Haakon, Stromgald Scourge for a bit of persistance, especially when combined with Mirran (or even Phyrexian) crusader. Seems like you have a bunch of ways to put him to his beloved grave... I guess there are plenty of cards that will abuse the tribal topic - e.g. Swarmyard,...
Third - is there any chance of beating combo? You should squeeze at least any discard (Inquisition of Kozilek etc.).
In your colours, Cold-Eyed Selkie will benefit from same effects as constable ;-).
The suggestion of Geists is kinda obvious. Another option for 3CMC beater could be Mirran Crusader, or at least in the sideboard. Unfortunatelly he's vulnerable to Path to Exile and Lightning Bolt. On the contrary he's Abrupt Decay and Dismember-proof ... and double strike counts.
Besides that a few enchantments come to mind (though less aggroish, perhaps as a sideboard agins tron and such) - Sea's Claim, Convincing Mirage, Spreading Seas...
Further, Gitaxian Probe is not bad in this kind of deck.
PS: You'd better replace Unsummon with Vapor Snag.