This is just a random Idea but what if you were to make the Itch.io archive a launcher that then would download the game & keep it updated? that way the size limit in Itch.io would be a non issue, and the players still could install & launch the game from the Itch app...
The issue is not download speed, it is about organization & version control, one reason Steam is so big is that is a central hub for most of our games, easy to install, keeps our games up to date, and even stores saves in the cloud, my hope is that the Itch.io app could do the same, in this case, what I want is auto-update feature.