currently it is impossible to connect to a mac using apples's builtin VNC and using option key, at least not without sacrificing either alt or windows keys.

(having alt double as alt+meta as in default config won't work for VNC-connections)

combining meta with compose is a good combination, as you can trigger compose/multi-key functionality with shift modifier, and since you don't keep pressing you have both lowercase and uppercase letters available for the composing.

It is important to have meta available without additional modifier, as otherwise translation via vnc won't work properly, but PC laptops don't have dedicated meta key, and laptops keyboards don't necessarily have right win/menu/alt (or alt is needed as altGR/iso-level3-shift already). The available options all apply to the left ctrl or win (or both alt/win keys) that should not be sacrificed for that..

######
so please make

partial modifier_keys
xkb_symbols "rctrl-meta-compose" {
    key <RCTL> { type[Group1]="TWO_LEVEL", [ Meta_L, Multi_key ] };
};

available as a default compose/misc option.
I fail to see how I could add that locally, without overriding evdev rules files (see also bug 96641)