Sadly I'm rather skeptical they can make it to 5mil even though Kickstarters usually ramp up near the end, but a few more stretch goals should be able to be met.
Plus I'm really not sure what they could offer at 5mil that would be realistic but also enticing to a wide variety of the people interested in the game. I get the feeling something like a level editor is just my dream and most people wouldn't care; also I tend to forget that a level editor for a 2.5D game is much more problematic and complex than one for a purely 2D game, which is a far simpler affair. Offering 2D art even at 5mil simply wouldn't be realistic especially given they've committed to 2.5D.
I was hoping one of the goals would be to bring some ex-Konami devs from the GBA or DS games that IGA knew on board, but I doubt that would excite too many people, and it looks like it isn't happening. The vast majority of people don't know much about the people who worked on those games besides IGA, but they had an impact in making those games what they were.
Also I'm a little worried about the mini-game, as a mini-game by its nature -- if it's of the same genre as the real game -- is going to tend to be less impressive than the final product and the exploration would definitely be gimped by the small scope. If that results, it may harm the sales of the final product. If it isn't similar in design to the final product though it could give people the wrong idea about said final product and harm sales that way. It's definitely not something I would've come up with for sure.