It is not the math classes where I'm worried that this would be a problem, it's in the engineering courses. There's a few situations in mechanics/structures/materials that I can think of where using ∆ instead of the existing 3 notations would become nearly untenable. In these circumstances each "line" of a solution/step usually took the form of more than one page.
∆ and δ have distinct and separate meanings in some of my coursework that can't be exchanged. The nomenclature/symbolism is so screwed up in some engineering fields that it would either require all students to revert to the existing symbolism or a level of investment in rewriting literature from research academics that created this screwed system in the first place.
I think Feynman had it right, he could invent the best symbols in the world for every operation but no one will use them.
∆ Is used for delta's so frequently that I could see some nasty issues arising in notes for higher level maths.
I think this could be an excellent teaching tool, to be honest I sometimes pull log notation back into exponential with a variable if I can't remember it immediately, but I think this guy didn't read Feynman's biography where he discusses the problems with creating notation.