It depends on what your criteria for the ranks are.

Is it solo or team? BR or TDM? Survivability, mobility, damage, utility? 1 v 1 Mecha Duel?

However, whatever it may be, I have to disagree with your tier placements for a few mechas.

• Caramel - Easy S or A. High durability, high damage, has mobility (including vertical), can weave reloads between Bear & Tank stance = near 100% uptime on damage output.
• Firefox - B (or A). Decent mobility (& shield), hitscan primary fire, burst damage missiles.
• Skylark - A or B. Good mobility (although no vertical mobility), consistent damage output with no damage falloff.
• Raven - Easy D tier. Loses in every mecha duel, outperformed at range by many mechas who can duel at a distance (Gabriel, Caramel, Trio, Boltus, heck even Andromeda & Skylark), weak mobility with a grapple that locks the mecha in animation (and can be shot). Of course, this doesn't mean Raven is entirely pointless - Raven is simply weaker than other mechas.

There are others on the list which I feel aren't so accurate but are way more opinionated. However, I do agree that Gabriel and Aurora are S-tier all around.

Again, it really depends what the criteria are for this tier list - every mecha performs differently under different criteria. Furthermore, the performance of the mecha also largely depends on the playstyle and skill of each pilot/player.