You've explicitly stated several times that Charis isn't going to be in the tournament. This, despite several suggestions about how you could involve her through PL boosting. Unless your opinion on that has changed since then, I'm going to assume she's not in the tourney.
Tiamat hasn't even been created yet, beyond the basic skeleton of what she is, so unless you have plans to introduce her as a contestant halfway through the tournament arc, it's safe to presume she's also not in the tournament.
Thess is explicitly on his way to enrol/be enroled in the tournament, so that's one PC contestant. He's also explicitly not allied with the Arcosians, which we both agree on.
There is nothing to suggest that Glacial has any plans to enrol in the tournament itself, instead focusing on his desire to challenge his father to combat. Since there is nothing to otherwise suggest he wishes to engage in formal combat within the actual tournament at this stage, I am going to assume he is not going to be involved in the tournament proper.
Azamat is present at the colosseum, but so far hasn't shown any apparent interest in joining the tournament, and is known to have his own plans regardless. Until further notice, I'm again assuming he won't be fighting in the tournament itself.
Luceptor and Expial have both signed up already, so there's three PC contestants. Of them, Luceptor's allegiance is primarily to himself, and secondarily to the Makaioshin as a whole; at this precise moment, he has no particular reason to consider himself an ally of the Arcosians, and therefore isn't. Expial currently has no allegiance to anyone, so he can't be counted as an Arcosian ally either.
Lord Shiver's personality and biography haven't been filled in yet, so there's not much about him that can reasonably be assumed beyond "he's the Blue Clan leader"; however, what is within capacity to assume is that it'd be poor form for the leaders of either side in the truce meetings between Earth and Arcose to actually enter the tournaments themselves, for a variety of reasons. With that in mind, and again given that Shiver presumably has other plans beyond the tournament's bounds, I figure it's safe to assume he won't be entering into the tournament either.
Glacier likely won't be entering the Galactic Tournament for the same reasons as Glacial, being preoccupied with challenging their father to a duel to prove non-shame, and no suggestion of entering the tournament has yet been made in any case.
There is no good reason to assume the Android will possess the capacity to enter the tournament with any expectation of victory in the short time period available to it, even if one assumes that it manages to find out that there's even a tournament going on before then. It's been implied that much of its story arc will take place on Earth regardless, at least early on, but either way, entering the tournament currently seems to be far out of reach for it.
The only wild card I can think of is Harkon, who may be compelled to enter the tournament by the voice in his head that was previously Limac. However, since it has not yet been suggested by
@Halvtand that he will enter the tournament at any point, I cannot assume he will do so; thus, I shall assume that he won't for the time being, and even if he does, he certainly isn't affiliated with the Arcosians at this time.
Thus, we have Thess, Luceptor, and Expial who are definitely going to be part of the tournament, with no other characters having any solid suggestion that they will also join the tournament at this stage, and as I've said before, I therefore cannot assume they will join the tournament at all. Saiyan plus Makaioshin plus Majin equals three PCs, none of whom are allied with the Arcosians. I have made certain beyond any reasonable doubt in my mind that this is the case
at this moment, given that the uncertain cases mentioned where a currently-unenroled PC might enter the tournament for some reason or another, as well as the situations I listed with your characters, can be accounted for in future listings of who is and is not a part of the tournament; if I have missed something critical that affects these results, then by all means, please do tell me what I've failed to account for.