How dare you try to poison people with flavour! Everyone knows a proper cucumber sandwich is a single layer of cucumber slices (skin removed) between two slices of white bread (Use as a guide). If you're feeling particularly daring you may add a small pinch of salt and pepper but be careful not to over season, you wouldn't want to make something tasty by accident!
This is why the English have to claim half of the food their immigrants brought with them as their own, lest they look up and realize the only tasty thing they make themselves is deep-fried (and even then that's arguably Scottish).
Shitlingford here is right though, it's an old ingerlish tradition to pillage any establishment that serves nonwhite food and murder its occupants. Probably triggered some memories of visiting "the Indochina" during his Oxford years.
The point of a cucumber sandwich is that it's light and
refreshing. You can eat it as a snack while drinking tea, and not worry about not being hungry later.
What you suggested sounds nice, but it's a meal and that's not what they're for.
I think this may have strayed too far from its origins as a poverty food. White bread, butter, cucumber and mayonnaise (if you're fancy) paired with some weak tea drowned in milk is a perfect way to save money so you can afford to have a TV license to watch England lose at football or splurge on Wensleydale Cheese to eat with your Christmas fruit cake and Christmas goose or go to Ibiza and get horribly sunburnt while complaining that the Spanish people are speaking Castellano.
Plus it helps keep you thin so you can fit in chimneys to sweep.
Of course the jellied-eel brained colonialist wants to burn the entire place to the ground because there's some flavor added. The over the top violence in response to scary others being otherly fits the British Imperial model.
It's funny because you're not even getting into exotic ingredients with the most far out being what? Sriracha? Cilantro? Ginger? They didn't even suggest MSG that scares everyone off. You're not pickling with rice wine vinegar and sugar (though I think you should) You could probably serve that shit in the bible belt and people wouldn't look twice.