The two obvious choices have already been mentioned
it's either
(a) a temporary building that will appear dring easter and you use it to complete easter quests - similar to the Golem but helpful rather than an "enemy" to be defeated
(b) it's a permanent building that can be bought with easter eggs - probably a residence, although there could be other options
My vote is for option (b), and that it is used as a residence
But I think option (a) is a great idea to be considered for future events. Something fully thought out and well implemented that isn't just a resource sink .