I'm the opposite: I think
Gwyneira fits much better with
Theodora and
Hermione.
Alastriona sounds over-the-top and silly, IMO.
Gwyneira Simone and
Gwyneira Elizabeth are pretty. If I had to, I would use one of those. I'm not sure about a second middle name, and I'm admittedly not very good at making combos with more than one middle name. The only one I can think of from the names on your list is
Gwyneira Elizabeth Cecile/Cecilia. Could that work? :/
BTW, how do you pronounce
Gwyneira? I couldn't get a straight answer when I looked it up.
**Starfish and coffee, maple syrup and jam/Butterscotch clouds, a tangerine, and a side order of ham**