I have not seen Parade, nor have I actually ever listened to the score. Other than the ensemble Now You See Me, Eisenberg hasn't had a hit since Social Network. I think he would probably be excellent, assuming he can carry the score, but don't see him selling tickets in advance; maybe if it and he get mega-great-reviews, his presence will then help to sell tickets.
Of course, there are other questions that impact the possible answers: (1) non-profit or for-profit production, with limited or open-ended engagement? Scaled down production or Harold Prince scale? is there really any female box office attraction who would take the non-leading role, unless it was limited engagement and she wanted to show her chops?
I think Jake G would sell tickets, as already proven; maybe he could open it on a limited engagement, non-profit basis; and, if really successful, maybe Eisenberg would be a good replacement if there were indications that an extension without Jake G might be viable. Re an open-ended, for profit, I think it will need a star on the magnitude of Jake G. Not sure I can think of one who has the talent, the voice, is the right age, and has the star power to sell tickets in advance.
Of course, as proven, Daniel Radcliffe sells a lot of tickets, but he can't guarantee a hit. If he can sing the score AND the show and he get excellent reviews, he would then help to sell a lot more tickets.
IMO.