Although there already exists a veritable plethora of help with office suites (particularly for Excel) I do believe there is room for yet more, provided high quality, well indexed, user friendly, current and with a quick response to posts.
I also believe that the distinction between office suites is a lot less significant than many 'subjects' that are often deemed members of a single 'group'. For example, that many functions and formulae (the 'subject') share syntax and behave in exactly the same way in more than one suite and that [compile-errors] and [widows] (both valid tags at software.codidact.com, the 'group') are likely more different in nature.
It is also clear that for those struggling with office suites the particular suite for a solution sometimes may not matter very much. One indication is that, despite rarely being appropriate there, Stack Overflow [SO] currently has over 1,000 Qs tagged both [excel] and [google-sheets], some Qs with tags for three different suites, and even a few for four. Many users have access to more than one suite, possibly favouring Excel at work and Sheets at home.
I fear the problem with any site covering office suites is likely to be the quality of the Qs. It could become a magnet for help vampires. Many of the current Codidact sites might reasonably be termed 'disciplines' … but for the majority of office suite askers I have come across on the web 'rigorous' is very far from how they appear to me. I have the impression of a huge culture difference between most users of Codidact and most people with office suite issues. The former mostly seem to enjoy learning, the latter mostly to be focused on getting a quick and easy fix to a practical problem.
Since culture can vary across sites this difference may not be a big problem, but I think best to keep any 'Office Suites' site well apart from others. Thus overlapping scopes should be avoided. If 'Office Suites' is to cover the likes of GAS and VBA, then maybe exclude these from Software Development. Though I'd prefer they remain on topic there and instead simply have GAS, VBA, and equivalents off-topic at 'Office Suites'.
Then the issue becomes how to cope with a 'business problem' where the person asking is not aware that the only, or most practical, approach is to write 'code' rather than apply a feature, a standard function or a formula. Super User has migrated some Qs to SO in cases like that, and for similar reasons Web Applications has at times recommended asking on SO instead. I have also seen the opposite on SO – Qs where a VBA programmer was unaware of some standard functionality and needed help with writing code to replicate it. Such Qs have usually survived where drawing attention to the standard functionality was not the first A, but if the first A then the Q was quite likely to be Closed as off-topic for SO.
Perhaps 'Office Suites' would be viable if GAS, VBA etc were off-topic but the culture included no down votes for that reason alone, and an A (or canned Comment?) to the effect "A practical solution requires coding with GAS, VBA, or similar and hence the Q is off-topic here. Please delete this Q, though you may want to copy it prior to re-writing it for Software Development first." was deemed valid.
There is lots of advice about specific features, functions and formulae but very little about combining these effectively. I think users would appreciate if the person answering could be free to choose which suite was most suit[e]able, be allowed to combine package elements where that makes sense (e.g. 'subcontract' some of the 'Excel' processing to Word), and choose how to mix features, functions and formulae for a practical solution. Despite the plethora of help in general, I am not aware of any site offering this mix to any significant extent. 'Office Suites' might be almost unique and very popular.