The mousefolk in particular are known for their pluck and bravery, and when the call to adventure comes, they tend to answer
The going rate for 4/4 hasty fliers is , so losing haste at the cost of but with an additional toughness is acceptable
Just like Command Tower, Arcane Signet is a card every casual Commander deck needs
Also, as appealing as trying to pair [Card]Gilded Goose[/Card] with Emry is, your mana dork turning off after you cast [Card]Rogue Refiner[/Card] turn two isnt really acceptable, and being unable to crew [Card]Smugglers Copter[/Card] is a big hit
You don't have to spend another mana just to get the extra ability
Ruthless Ripper is a neat one from Khans of Tarkir that can morph face up without mana, so it makes sense the design of disguise keeps room to grow