Hello, enjoyed lurking my way up til now reading this thread but felt like putting in my 2 coins.
I have been a long supporter of Isaac getting added, was pleased yet disappointed back when Brawl showed he was an Assist, assumed he'd be added in future ones, got further disappointed once the final chars were revealed in Smash 4, but I'm still holding out hope.
While reading, I had a thought about something that wasn't discussed much, being PP. It's possible that they may include PP in the game, with Isaac having to "walk around" to recharge it over time.
I also figured it's likely there would be a boss or two added, the Kraken or the Tornado Lizards might be fun options.
![Stick Out Tongue :p :p](/styles/default/xenforo/smilies/tongue.gif)
Or you know, some of the more obvious ones, Saturos, Menardi, Dragons, Dullahan.
Stages, beyond the ones already mentioned... Tolbi bound ship and Gabomba Statue pop into my head a little.
I could definitely see the Hand being Isaac's grab move. Meanwhile, a move I haven't heard much talk about is Force. A fist that forms and shoots straight forward sounds like an easy transfer into a game like Smash.
Anyway, those are my thoughts. One day the stars will light and the sun will shine.