Screen filling overhead message

I’d like to display some reminders with big, bold, screen filling overhead messages that everyone can read even from distance in a comfortable way.

In the past I used growl to send this kind of messages, and I could continue using growl, but wanna be independent from dependencies, if possible

Mac 's own system notification are way too small with those little banners and doesn’t do the job in this case. Some suggestions?

When Apple doesn’t install a buggy update I use such script:

use AppleScript version "2.4"
use scripting additions
use framework "Foundation"

set {theYear, theMonth, theDay, theSeconds} to {year of (current date), 1, 1, 0}
set theCalendar to current application's NSCalendar's currentCalendar()
set begDate to theCalendar's dateWithEra:1 |year|:theYear |month|:(theMonth as integer) |day|:theDay hour:0 minute:0 |second|:theSeconds nanosecond:0
set timeDiff to begDate's timeIntervalSinceNow()
set nbDays to (-timeDiff as real) div 86400 # (24 * 60 * 60)
if (nbDays mod 2) > 0 then
	set theAlert to ((path to me as text) & "Contents:Resources:vider le déshumidificateur.rtf") as alias
	tell application "TextEdit"
		open theAlert
	end tell
end if

It’s executed everyday when I boot the system.

It display a document filling half the screen.

Yvan KOENIG running High Sierra 10.13.6 in French (VALLAURIS, France) jeudi 26 mars 2020 15:04:24