Obviously you wouldn't completely remove the speed cap and just give random heroes infinite movespeed. But it's stupid that there can't be heroes moving faster than 522. Rampage is a perfect example; his charge should definitely break the movespeed cap. This could apply to a number of other melee heroes and future heroes as well. The only hero I can imagine moving too fast that would be broken is Flint, due to his ability to outrange people. Everyone else has to get in range of slows and stuns to fight anyways, and only a tiny number of heroes can even break 522 speed without resorting to some retardedly weak build like tele boots, firebrand, marchers (With the tele boots, yes) and euls. The only reliably fast hero I know of is pest, and he'd hardly be broken going at 560 instead of 520, especially if he was missing blink and tank gear. Hell, you could give a hero 600 movespeed to start and he still wouldn't be broken (Or even very useful) if that's all he had. Having an arbitrary hard cap is just stupid.
Creep stacking is just a weird bug that got left in because certain heroes would be useless without it, but it's an enormous part of the ricing game. It basically allows one hero to spend the game farming all 3 lanes and the entire forest without missing spawns if done properly. Obviously you can try to interfere with this and nobody ever does it perfectly, but the potential there is just stupifying. It'd be like allowing gold or item transfers between heroes. It's why everyone does trilanes at the top end now. In the span of 20 seconds a hero can stack 3 camps, effectively giving those 3 camps to the carry, around ~300 extra gold and maybe 500 xp. And this can be done dozens of times a game, while the ward bitch is out throwing up wards or whatever.
Shrunken head is just an example of an item that is purchased in pretty much every game and dilutes the variety of play. Same with wards and boots, but wards are at least limited in purchasable number, like puzzlebox (And Kuldra, among a lot of unofficial rules). People always rage at the thought of making boots more expensive (And it would indeed change a lot of shit) but the game would be much more interesting if boots weren't a given on every hero in the game. You could have a hero without boots but relies on blink and allies to be in the right position, and makes use of the extra damage output the slot and saved gold afford him. More possibilities = more interesting and complex game = better than playing tic-tac-toe. It's stupid to balance all the damage causing items so they all see some play, but just allow shrunken head to be the be all end all of magic defense for a carry. On the other end of the spectrum we have items like the codex and staff of the master on most heroes, which only complete morons buy thinking it's the best use of their gold.
Magic armor doesn't stack from items, even though there's no real reason this should be the case. Someone with 4 mystic vestments isn't unstoppable and overpowered. But it works like this because WC3 did and change is bad. Someday someone will make a game on this template without using dota as a crutch to balance around, and not fuck it up terribly like demigod did. And it will be glorious. Not going to happen from HoN though.