How do I configure a personal Gmail account to act as the client for my company provided O365 email account? Would it simply be a matter of setting up SMTP / IMAP, or is it more complicated that that (or even possible)?
This should be possible using POP3 (incoming) and SMTP (outgoing). Gmail cannot act as an IMAP client AFAIK.
Gmail can retrieve up to 5 POP3 accounts and Office 365 would seem to support POP3. And you can configure Gmail to send email as your O365 email address, using your O365 SMTP server. From the above link, these settings would seem to be:
However, possible caveats with this approach: