1) The 100 HP buff to Hoplite only is because they should not have 200 HP less than Mongoose, especially because Mongoose can also benefit from mobile shields, and Mongoose don't die to 2 sera bombers. 550 HP for Hoplites is a good number, not too high, not too low. Mongoose don't need more : they already have much more.
2) Speeds: 3603 introduced these heavy speed nerfs for some unknown reasons. But 3603 is not a bible, remember navy buildtimes. Speeds in 3599 made much more sense. My proposal are still below 3599 value. Speeds were all much higher than in 3603 (pillars and rhinos = 3.3, Obsidian = 3). All I'm suggesting is to almost go back to 3599 speeds.
Just because a unit says "heavy tank", doesn't mean it's a slow unit. Rhinos and pillars are said "heavy" because they are t2, but they are actually medium t2 assault units, Hoplite and Mongoose are light units; Riptides and Wagners are heavy assault units and yet they are much faster.
2.7 speed is really slow when you compare to t1 (3.5 speed average) and t3 (Siege bots have speed 4; harbingers, sniper bots are 3, Othuums are 2.5; onlu Bricks and Percivals are significantly slower than Rhinos and pillars, but have much more range and hp). I can't argue with people who think it's normal to have medium and cheap unit that much slower than anything in the game when the supposedly heavier t2 units are much, much faster. For me, it's ridiculous. I know the purpose of high speed hover units is because ships are very fast, but I fail to see why t2 normal tanks, that are weaker, should be slow as snails.
The rhino is probably the worse tank because of its slow speed.
Why should Rhino have 1.0 less speed than mantis? How can you use them efficiently like that with their shitty hp and range? I'm giving a tip to Cybran players : forget about rhinos, build wagners, they are much better in all aspects.
If you prefer that I suggest only it for Rhino, which is the most completely useless t2 unit currently, I'm ok with this, but you should compare t2 speeds with other tiers. It's a matter of general equilibrium between the tiers.
Last argument : the higher speed is also meant to help escape ACU overcharge, the bane of T2 units.