I kind of disagree a bit here.
Remember, 10 Mb is already a lot to download on a little internet connexion. (mine for example => 60 Kb/Sec AT BEST)
Such a game already takes quite some time for me to download. And often, when I want to test a game in the arcade, I don't want to have to wait 15 minutes for it.
Also, more space doesn't mean more levels.
You can very well reuse the same textures/objects and still provide long and interresting content.
It's also part of a good coding practice to be able to reuse code and ressources at the maximum so that in the end the user is the winner (I'm provided with 10 levels, even if they use the same textures, but I only downloaded 1 set of textures once, quickly)
I hope you see the point I'm trying to make here.
Also, with image compression in C2 it is possible to stock a great deal of textures in 10 Mo.
Finaly, it's not because you propose a 15 hours long game with full HD pictures switching at every level that it will be necessary a good experience for the user (keeping in mind the downloading factor from earlier for example)
Space/size isn't really an issue here.
Also remember it's 10 Mo ZIPPED.
Even if you can't win much over already compressed files, it reduces the size of your event sheets/levels greatly.