The larger part of the existing outlook tags (approx. 60) should remain as they are. Many of them relate to the native Outlook, often in combination with the web based Outlook or Gmail.
The new questions, about Outlook.com, should be re-tagged accordingly and reviewed. If many haven't been changed, we didn't pay attention during the review process.
The simplest solution would be for someone to retag one question with onedrive then we can merge the tags.
This will have the effect of retagging the rest of the questions tagged skydrive and automatically convert "skydrive" to "onedrive" when anyone uses it on a new question.
This has now been done.
To do the rename you have to merge the tags which seems to have had the side effect of merging hangout and google-hangout into google-hangouts as well.
The cache takes a little while to catch up but if you spot any weirdness after a couple of days let us know.
A terrible idea and synonyms would not work for this. The most I would contemplate is a solution that has been applied on Stack Overflow where I wanted to address a similar issue and google-spreadsheets-conditional-formatting exceeded the character limit. So now gs-conditional-formatting is in use there, following the precedent set by @Mogsdad with gs-...
Here's how I think we should fix this.
Get a good excerpt and tag wiki for g-suite
Make google-apps and google-apps-for-work synonyms of g-suite
Make google-apps-email a synonym of gmail (as suggested in this question)
Google Apps Sync is now G Suite Sync for Microsoft Outlook. Therefore, rename google-apps-sync to g-suite-sync. (I would suggest g-suite-...