I have a concern that if you allow the PCs to raise the spirit of Ethan Allen, they would be breaking one of the laws of Magic (I don't recall the number). As its only a Con game, that may not be such a concern for you, but I'd hate to be a player new to the system and do something cool - like raise the spirit of a dead Revolutionary War hero - and then try to pull off something similar in a new campaign only to find out I broke the law (maybe) and the Wardens are after me to try me and execute me.
Am I remembering the Laws of Magic wrong? And I apologize for being "that guy"...you know...the rules lawyer...
...Unless, of course, Ethan Allen wasn't actually human, and was instead an immortal of some sort from the Nevernever...then there are no problems with violating the Laws of Magic, only consequences for summoning something from the Nevernever. Perhaps he'll need a boon from the PCs in the future in order to secure his aid? Or at least from your NPC in case you are going to run another con game next year - continuing storyline.
