Since there is no use for A00, that I know of, maybe let it just retain the last arpeggio effect amount value? It could work the same way that the portamendo effects do. It’s very logical and will save a lot of tedious keystrokes when using the Axx effect (spamming an arp, or only having to change it at one place).
Obvious idea is obvious. Why I didn’t request it before, I don’t know. I’m pretty sure some other tracker thought of it already.