First, I don't see any reference for how it handles weapons below tier in the submission beyond a vaguely stated "and vice versa" which may or may not apply to this. All conversions were Tier+0 or above, though some went back and forth. That's part of my problem.
Also, my apologies, some corrections. The ship has two kinds of turrets, most of which are Tier-4 and four of which are 2 below Tier -2. Here's a reference.
2D (Current Standard):
2E (Refit):
Plumeria 2D has 1 main gun at Tier+2, 2 canons at Tier+0, 2 missiles at ~Tier+0 (has used up 8 slots at this point if the missiles count), 4 turrets at Tier -2, and 11 cannons at Tier -4. This might just barely squeeze in as 10 slots depending purely on interpretation of how the Lower Tier weapons and the missiles are computed. Also, are individual missiles mounted to the ship counted in the total as I've done here? If so, starfighters might not be able to carry them anymore.
2E Refit has 1 Tier+2 main gun, 4 Tier+0 launchers, 8 ~Tier+0 missile tubes (only two face any given direction, rather than having 2 multi-axis launchers. Are these calculated as two weapons for this?), 4 Tier-2 turrets, and 15 Tier-4 turrets. This uses up 10 slots (depending purely on interpretation of the missile tubes), and then there are the turrets.
It should also be noted that the Plumeria is considered Tier 11, but barely fits into Tier 12 measurements...likely because its main gun consists of much of the front of the ship, and removing the gun entirely would make it a Tier 11 for more realistic armor considerations. Does that mean that the main gun doesn't count toward its 8-10 point limit since it is literally constructed outside of the Tier 11 ship's boundaries? Should the ship should be calculated as a Tier 12 for weapon purposes under this system? This is an example of the kind of questions we'll run into if this is adopted as-is.
I also know that the Chiaki is in the same boat, fitting well into Tier 11 even though it's labeled as Tier 10. I'm planning to make a Chiaki variant with Sakura-like attributes (including a main gun spike that makes it longer) in the future that this all may impact notably.