The problem stays the same: you need a real webspace for at least part of it...
-- and you don't want to maintain this list and the 'normal' store-website manually - they need to be created dynamically from the same data or they will get out of sync quite soon...
So yes: possible and not even hard to do - but not easily to do for free.
--> that's the whole point. If someone has webspace with cgi/node/whatever laying around he can easily do that.
(I could even do it in Ada - but that would need at least a vserver...)
Another approach: use a different extension than '.zip' for app-packages - than you could probably install an app with a filter for this extension...
--> clicking link on store-website would install the app ;)
--> this way the store-website only need to be adjusted for phone's browser.
Another approach: create a 'specialized browser app' which loads the website and intercepts the clicks on links for an app - so it can install it...
There are many ways to do it - not all of them are as good as others... :D