I do not expect the online version to ever have the same features. Even the Mac desktop version does not have the same features.
The online version is free and MS wants to be paid. It is handy for users but is not really a substitute. There have been numerous reports of corruption of numbering by using the online version on documents with multi-level numbering. I would recommend that customers use the desktop versions for any editing.
Even if a subscription were required to use it, the underlying web structure is such that the only way they would have parity would be if the desktop versions were downgraded to match the limits in the web version.