> I know 彁 isn't real: but it still insists on a pronunciation: ka in Japanese, (gē or gé Mandarin).

Huh? How do you pronounce 切?

> And it hints at meaning: bowed weapon, sound, elder brother; but your guess is as good as mine!

Why is "elder brother" a meaning hint if you've already assumed that 哥 is the phonophore?