Baron was probably more popular, but that undersuit is an entirely different design that it would need a new mold.

Kachidoki Gaim could work too with a few part swaps

I think you overestimate just how much work a Premium Bandai repaint can do... like, for starters, Gaim and Baron don't even share the same undersuit. I can't think of many parts they do share beyond the shin armour? It'd be impressive enough if they did Zangetsu considering the sheer amount of different parts there

Considering Preban puts out all-new kits often, I just won't be too surprised when something like this comes up.

I mean, so far for FRS Rider the limit has generally been 'black repaint with little to no parts'. Genm, Amazing Mighty, Joker; they're basically the exact same release as the originals with like 5 new parts (which Ryuga, Proto Drive etc would also follow). They pushed it a lot with Den-O's forms but that's because they were able to take advantage of the armour gimmick and it's Den-O; unless the line expands more by the time they get to Gaim I wouldn't expect anything like this

For folks in the UK, Kuuga Decade version is available at Gundam Mad for £35
https://www.gundammad.co.uk/product.php?productid=19787

I finally got Ryuki in today. I started building right away. Will probably do Dragreder tomorrow.

Another great kit! Though I wish the red of his eyes could be more visible.

https://i.imgur.com/OzUfvB4.jpg

Finished the Dragreder.

https://i.imgur.com/mbUBc6M.jpg

Here's the full gang. Every primary rider released so far.

https://i.imgur.com/bK8NPiU.jpg

Yay, 11 more to go

Very beautiful!

That looks gorgeous, I'm still waiting mine x)
By the way, I saw some customizer using some type of red paint that you could use for the eyes.