Your proposal seems good but:
1) -l for localness should be applied on the menu definition, not on the alias callsite. This would make it match up with other locally defined features, like alias -l and dialog -l.
2) I like the proposal of having multiple arbitrary menus specified in a popup, but I'm not sure if this is technically possible. If it is, though, I'd propose having an "unlimited" amount of arbitrary names:
/hotlinkmenu channel HLMenu OtherMenu ...
They would be appended top to bottom in the order they were provided, so channel would come first, HLMenu next, etc.
3) I still think the name /popup (or /createpopup) is better/more generic than /hotlinkmenu-- specifically because this would allow users to create popups in other situations as well (dialogs, left clicking on custom windows, etc). It is not a functionality that's necessarily coupled to hotlink events.