Given they would end up likely being upgraded Toa, as I'm sure they mentioned the idea of sticking with the main team, I'd want to see them either mutated or given a theme that drastically alters their appearance.
I've joked about this prior with members, however given the new Star Wars pieces and seemingly 'smooth' leg pieces, I would be interested in seeing the Toa get a sort of 'environmental suit' to explore other locations. In essence a combination between the Bionicle Exo Suit, Bionicle Mahri and the Hero Factory XL sets.
Which would result in something like this, just using a lot less pieces;
This could allow for new masks, new armour pieces, larger sets and emphasise the idea of adding to the sets to improve them.
In addition, worried new Toa at this stage would be pointless, given we barely have enough character development to account for these Toa, let alone an entire new team who would all need development.