I work in scale only when I have no other choice. 99% of the time I am making my artwork at full size. CorelDRAW and Flexi both provide a lot more breathing room than Illustrator. The max art board size in Illustrator is currently 227" X 227". Back before Adobe re-built Illustrator on PDF technology at the end of the 1990's (it was a purely Postscript application before) the max art board size was only around 10' X 10'. Adobe has received a ton of user feedback regarding the art board size limits, but I don't think they're going to do anything about it anytime soon. That's going to leave Illustrator users stuck with using some kind of scale percentage on large designs.
CorelDRAW has a 1800" X 1800" max art board size, but page sizes above 1000" will often bring up the pop-up message "this zoom has exceeded the boundaries of the drawing space, your window will be adjusted accordingly." Flexi can go bigger. Unfortunately Flexi does not draw with the precision level of CorelDRAW or Illustrator. Plus Flexi is stuck clear back in the 1990's with its outdated type handling. You can't do squat with elaborate OpenType font character sets in Flexi.
I really do not like applying scale percentages to rulers. CorelDRAW allows this with its "Edit Scale" function. The end results can be all over the place when that CDR file is opened in a different version of CorelDRAW, opened in CorelDRAW on a different
computer or exported to a different application. What I mean by "all over the place" is the artwork often doesn't blow-up to full size accurately. It will be off a little or even a lot. The function is just not anywhere near as reliable as creating a much bigger artwork and simply designing at full size. If I need the full size artwork represented at a certain scale on a printed sketch I will copy, paste and reduce the artwork to size using a specific numerical percentage that delivers 100% accurate results.
I suspect a third party plug-in for Illustrator that monkeys around with the rulers could be prone to the same issues I see in CorelDRAW. If I design at scale within Illustrator I will not alter the rulers. I'll just include a big loud label in the artwork itself that it is at a specific scale, like 1" = 1' or 25% actual size, etc.