This means having an API and usable connections to existing online services. I'm sure the vendors of such services would support it. So a user could simply install LyX, and benefit from the newest TeX version without installing it - slim but capable and up-to-date installations would be possible.
File storage services such as dropbox could be connected, the storage of an online compiling service used, or files could simply be uploaded each time when being compiled - LaTeX files are small, and compressed uploads or syncs would be quick.