Ok on the programming template it wouldn't really be adding options but adding limitations since turning radius it self would be limited by speed of the camera like in 1.0 and only the physics/animation completion forced set parameters on that when stopping less so on when mounted then on foot.
Here is the logical perspective of the vanity system. As a player to receive the good armorers one still have to go dungeon diving, quest completing, uppercutting dragons and the like to get the pieces but if they choose not to display it is not effecting any other player as they can be scanned and in pvp vanity items will be turned off (Which is more to stop people from hiding what they have but I am assuming if I am playing at top tier that if this guy has an axe but he looks like a bum he is war armed to the teeth but that natural assumption may just me). So the vanity system is actually not taking anything from anyone and it doesn't give an advantage because the person would have to acquire the said item to ware it. That is much different then a vanity system like DCUO where you are collecting set styles instead of wearing a specific owned piece like in spiral knight.
On the mount thing having each one specific traits of movement isn't really sound, not so much because of the development but just because when traveling specially with other members of your party/ LS why should you slow everyone down just because you wanted to ride a mount you worked "hard" for. In Wow and in SWTOR the mount system was actually a leveling treadmill/money sink system in its own right so the ranges were set and no one would ever go back down the line because they would loosing benefits. Which there is nothing wrong with that per-say but the rental vs owned speed difference is really enough of a benefit because a mount as a trophy is a goal enough for people to chase after. And not punish those that are not able to play long enough to complete what they want and get the mount to fit in.