Hi! Your list is intriquing as the items are so different.
I had to think about my sugestions as this was a tough case! I like tough cases though, so I analyzed extra hard for you!
Here are my thoughts if I may...
First, based on your collection and list, my guess is you do not require matchy matchy sets.
If you do require a matchy matchy set, I agree with the others and say get the Lotus earrings. They will be perfect with your Lotus ring. I have the Lotus ring and earring set as well as the Frivole WG pave BTF ring and earring set. I thought I could wear the Frivole WG pave earrings with my Lotus ring, but they do not go. I ended buying the Lotus earrings to create the set, and I love the set.
That said, if you do not feel the need to match your Lotus ring with the Lotus earrings, I would not get the Lotus earrings or any of the items on your list.
I would recommend getting the Frivole Large WG pendant. Why?
Looking at your list, it seems your style is a preference for metal pieces.
You also said you wear your HP pendant and your WG Frivole earrings the most.
You mentioned diamond earrings (I am assuming the Lotus earrings) would be reserved for special ocassions.
For the reasons above, I think the Frivole Large WG pendant would look fabulous with your WG Frivole earrings. A beautiful shiny flower! I also think the large Frivole size is very different from the WG guilloche pendant.
Most important of all, I think you will wear this pendant regularly.
I have a gut feel you won't wear the items on your list regularly.
You said don't really wear bracelets, pins will poke a hole in your top, Magic pendant might be too long, and Lotus earrings are too dressy. All these comments make me think if you get any of these pieces, they will just sit in your jewelry box, and it will be such a waste.
For me, no matter how much I love a piece, if I will not wear it regularly, I pass. Jewelry is meant to be worn.
That said... what do I really recommend?
I know you said you do not really wear bracelets. However, I think a diverse jewelry collection should have at least one classic bracelet. A bracelet will also enhance the beauty of your ring.
For me, I love bangles. They are clean and look crispy on the wrist. They make a statement, yet because they are crispy, they do not compete with a ring as some link bracelets can.
I think your collection would be fabulous with the WG Signature bangle. It's clean, yet shiny. It would go great with your Guilloche pendant and Frivole WG metal earrings. It would also look nice next to your Lotus ring.
If you can go bolder, the WG Clover is my #1 vote, but I think that look might be too busy for your preference. Bangles are also very easy to take on and off if that is a concern as to why you do not wear bracelets.
Just like a single watch & engagement ring on the left hand tie together to create a beautiful look, a clean bangle & ring on the right hand does the same to create a gorgeous look.
My vote would be for a WG bangle, no doubt in my mind.
Just my two cents. Hope this helps in your decision.
Sorry for the long post, but I did want to share my thoughts with you to help you decide.