Would you use combos such as:
[name_f]Felicity[/name_f] [name_f]Beatrice[/name_f] (Beatrice possibly means happy)
[name_f]Felicity[/name_f] [name_f]Alaia[/name_f] (Basque for happy)
[name_f]Felicity[/name_f] Letizia/Laetitia?
My favourite is Felicity Alaia, I don’t think the other two flow as well.
I don’t think you /have/ to use another cheerful-sounding middle, though you definitely could! If I had a Felicity combo I’d probably make it something like Felicity Bea, Felicity Pearl, Felicity Maeve, Felicity Marlowe, Felicity Ever or Felicity Margot.
Sure, why not! I like [name_f]Felicity[/name_f] [name_f]Blythe[/name_f].
I probably wouldn’t because I happen to know the meanings and it would bug me, but I’d say the majority of people wouldn’t know them, so I think it depends how much it would bother you personally.
Absolutely! I don’t see it as much of an issue imo - unless you’re outright naming her something like [name_u]Happy[/name_u] [name_u]Happy[/name_u] [name_f]Joy[/name_f] [name_f]Joy[/name_f], I think it’s fine 
[name_f]Felicity[/name_f] [name_f]Beatrice[/name_f] is lovely!
Totally, middles you’ve listed aren’t literal (not [name_f]Joy[/name_f] or smth similar), so it doesn’t feel like Too happy.
Personally no, because the matching meanings would bother me, but to be honest most non name nerds wouldn’t know, so i think you could get away with it