What can I say? It'd be one heck of a steamy relationship.
In all seriousness though, I can understand why people would want it to be there and all, but what they sometimes neglect to realise is that it's also essentially a gateway emotion as well. The above scenario was to simply point out that instinctually, the respective parties in question could prioritise the safety of each other at the expense of the rest of their teammates, but this is only one way out of many that things could potentially go horribly wrong.
Jumping sites for a moment, love, ironically, is also at least partially responsible for the differences between canon and the story of the BZPRPG. For those unfamiliar with that particular setting, everything from 2001 up to the first battle with Makuta is roughly the same, but with one key difference; Kopaka's unrequited love for Gali and jealousy of Tahu, due to his position as leader and (memory's a bit foggy in regards to this) his own personal relationship with her. Because of this, Makuta was basically able to convince him to pull a Vakama, causing him to betray the rest of the Mata at that one extremely pivotal moment, and thus leading up to the entire team essentially becoming his Shadow Toa generals. Needless to say, a lot of bad things happened as a result of this, including the deaths of not only Takua and every single member of the Chronicler's Company, but also eventually all of the Turaga as well.
Another issue I'd like to address is the child example from above. When I was younger, my mother used to tell me that the day you are born is the day that your parents truly discover that they are capable of murder, which, while not necessarily true in all cases, would certainly come into conflict with both the Toa Code and the main ideals of Bionicle itself. Sure, a Toa can act all heroic towards the beginning of the story by protecting their respective village and fending off Rahi, but once your standard Villain of the Week runs off with their kid and starts making demands, it's pretty much guaranteed that at some point, they're going to break out their inner Liam Neeson in order to ensure their safety. And if that wrath just so happens to be redirected towards another teammate or the people they're supposed to be saving, then it's pretty much a safe bet that the situation's about to go from bad to worse.
In short, while it theoretically could be implemented as a plot point to show character growth if done correctly, one would also have to consider the pitfalls of it's inclusion as well, and if the results of doing so cause the heroes of a theme primarily meant for children do things that are entirely unheroic, then it might be best to simply skip over its involvement when it comes down to forming the main plot.