That Matoran with a Vahi

Just something I'm wondering, but.

How far does a fan-work have to differentiate itself from Bionicle before it can be considered an original work inspired by Bionicle, rather than something based on Bionicle?

See, I've got this story project that I'm working on. It started off as just, you know, your typical reimagining of the 2001 Bionicle story, only with several things changed about a bit, and the characters as fully human. All good so far: but the thing is, while it's currently the furthest I've got on any project to date, and the one that I'd love to see through to completion... at present, I really need to instead be working on a project that's more of an original work, so that I can put my own name on it and include it in my creative portfolio - something that, as you possibly know, is frowned upon with fanart.

Since I've already deviated in my own way from the actual Bionicle story, I've been thinking of 'filing off the serial numbers', so to speak: replacing the key characters with original equivalents, making the setting a land of an quite different design, and pulling any other changes I can think of to make it stand on its own. While this seems plausible so far, the basic premise (six powerful heroes arrive on an island to vanquish a great evil), some of the themes (the MNOG climax's creation vs. destruction), and several other elements (e.g. Kaita fusion, Toa Stones, infected masks) still remain from Classic Bionicle. I'm not altogether sure if the differences I have so far are enough to push it into its own thing, or if it still seems hopelessly derivative of its source.

On the one hand, since I don't intend to directly make money off it, it shouldn't be a problem even if that is the case, as long as I credit it as my basis for the concept. On the other hand... I guess I'm still a bit worried that it may just come off as too much of a copy for anyone to actually enjoy it?

I dunno. I guess I'd appreciate thoughts, if anyone has them to share.