I'm not convinced. There's so little to your average assembly language that making the mnemonics longer won't help. With 6502, it would be totally pointless. You're going to be spending, what, 1 week learning this stuff, and then the next N years using it. You'll get used to it quickly enough. It makes more sense to optimise for experts, than it does for people who don't yet know what they're doing.

(And anyway, where do you stop? If you can't remember that STA means store accumulator and LDA means load accumulator, how will you remember what (&70),Y means, or what flags they use, or how many cycles they take? You'll end up with something like SUBTRACT FROM ACCUMULATOR MEMORY IN ADDRESS STORED IN &70 WITH Y REGISTER AND INVERTED CARRY FLAG WITH RESULT AFFECTING N AND Z AND C CLEARED IF BORROW AND V SET IF OVERFLOW TAKING 6 CYCLES PLUS PAGE BOUNDARY CROSSING PENALTY ;) - and even that probably isn't clear enough, because how will the poor reader know what the page boundary crossing penalty is if they don't know already?)

If you have something like x86's PUNPCKHBW, or POWER's rlinmw, and try to describe what they do clearly, you'll end up in even more of a mess. A one-volume instruction reference manual, sorted by opcode, with diagrams and pseudocode, would be far more useful.