@Gregg Groshon, Thanks for posting in Q&A.
From your description, I know you want to set the O365 default font to Calibri or some other installed font via Intune policy.
Based on my researching, I find a thread describe using PowerShell script to change the font. Maybe you can try to see if it can help.
https://techcommunity.microsoft.com/t5/windows-powershell/powershell-script-to-change-font-of-office-apps/m-p/2467840
Hope it will help.
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