What's the issue if you can't access MS Office offline? Does a remote server cause the problem?
Dumped M$ Office, Word, etc., for free OpenOffice and LibreOffice years ago and never had any problems.
You left out, updating received files and returning a modified MS format file. Interestingly, LibreOffice can read Microsoft Works documents and can save them as Word docs; something that MS Word cannot do.I'm a Linux guy. Dumped Windows years ago. Have been using free OpenOffice and now LibreOffice for years with no issues. Friends and businesses do send MS Office files etc., which LibreOffice has no problems converting over and opening. Worth giving it a try, it's free.
You left out, updating received files and returning a modified MS format file. Interestingly, LibreOffice can read Microsoft Works documents and can save them as Word docs; something that MS Word cannot do.
Excel is going to be the only potential problem depending on the feature set you use. There really is nothing with the power of Excel. If you're just using formulas in cells, it's probably fine. If you're using pivot tables, VBScript, complex conditional formatting, advanced filtering, or anything with PowerBI, there's no alternative.