These are my attempts at combination models for the toa and titans from 2004. They were meant to be coming up shortly after my Sentrakh and Shadowed One MOVs, but university got in the way. Sorry about the dust!
The Toa Nui uses parts from 8601 Vakama (missing his unique disk though sadly!), 8602 Nokama, 8603 Whenua, 8604 Onewa, 8605 Matau and 8606 Nuju.
Lariska uses parts from 8622 Nidhiki and 8623 Krekka.
Toa Metru Nui
A hypothetical look at what a Toa Metru Nui could look like, if we ignore the fact they didn’t have enough discipline to form a kaita let alone a nui before they became turaga, and there weren’t any toa nui in the main story. There was Krahka, so this MOC could be seen as an alternate version of that.
Goals with this MOC were to create a more cohesive combiner model, for a team which are in better control of their abilities. All the weapons are used, Nokama’s mask picked simply because it’s a different colour to the rest.
The separation of colours Megazord style still speaks to each toa retaining a bit too much of their own identity in the combiner though (besides looking cleaner), as well as the reversal of bushings on the left side. I see Matau as one of those people who leaves the crinkly part facing out. Heresy!
The gearboxes in the chest and shoulders connect up to make a load of gears turn. This can give the arms some momentum but there isn’t that much friction there.
Lariska
The goal with this one was to make a Lariska as she could have appeared back in 2004-2005, as a combiner model. As it’s tied to the prequel years, the MOC features both arms, but also has an optional robotic arm to replace either of the others with.
Apart from the robotic one, both hands can hold her throwing daggers (the left even has a mechanism to close the fingers around it). They can also be stored on her back, legs and, if you don’t mind ruining the collar, chest as well.
I may have let Mass Effect colour this one in giving her that Turian-style collar.
I can see some incoming flak about using the vahki head for her, especially since she’s meant to be able to wear kanohi masks - but Roodaka can as well so having this head shape apparently isn’t a barrier to that. Of course if I wasn’t combining two sets I’d be approaching the character differently!
I urge anyone who wants to try this not to include the original silver technic parts. I had a few of them crumble and shatter on me. 
