Thanks to Tech Electronics, DND ON, dwayneg, and BlackSunshine for all the input and ideas.
I was able to make all the tweaks work out. I can access to toggle into night mode via a phone or remote into my office desk to access the Mitel Web Portal (didn't know the web portal existed!), and I forwarded a port to the PBX to get to the Web Portal via outside the LAN as a third option (the jury is still out on leaving the port fwd in place.)
The phone dial in is the most robust manner for us to toggle into night mode from the outside since the dial tone provider is separate from our ISP. For our business, the internet is down more often than our dial tones (thanks to the consistently bad Comcast service). When the internet is down, I can still turn on night mode remotely.
I really should forge ahead to create a specifically "inclement weather" auto attendant scenario (like DND ON suggested - via phantom with forward paths and then manually forwarding them). When I start down that road, I will certainly look to the kind and taleted techs at this forum for help.
In parting I'll muse a notion I've always wondered about - the date (year) inputs for holidays. I know Mitel sells tens of millions of installs worldwide so it may be USA centric of me to assume the software would have built in repeatable "dates" for Standard north American holidays. Maybe not all holidays, but at least New Years, Christmas and July 4th perhaps (or just a "repeat yearly" toggle in the software). Having to input the next "year date" when a new year rolls around, for every "closed" holiday we have scheduled, seems unnecessary since an option to make a date "repeat" yearly could be an easy thing to program in the software. Perhaps I am overlooking such an "existing" feature??
Thanks again for all the assistance!
Ed