They're still highly experimental and could probably even be changed the next day.

I'm excited, yes, but I won't voice my opinion on the matter before I've tested it myself. All we know about the item are the stats and active but we haven't seen it in action yet and it may not even go through.

But in the State of the Game podcast, Meddler (and others) said they added too much mobility during the adc update. I think it's easy to see why the community is skeptical of mobility creep from items.

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I don't know if "lack of mobility" needs to be solved, but I do think that there either needs to be costs to mobility or answers to it for those who lack it, and my personal opinion is that LoL hasn't done a good job of putting appropriate costs on mobility in the last few years, and so I feel compelled to give champions that don't have burst mobility a few more of those answers to it.

Poppy's W is an example of an answer to mobility. "More mobility" is not.

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I don't know if "lack of mobility" needs to be solved, but I do think that there either needs to be costs to mobility or answers to it for those who lack it, and my personal opinion is that LoL hasn't done a good job of putting appropriate costs on mobility in the last few years, and so I feel compelled to give champions that don't have burst mobility a few more of those answers to it.

But it's going to be just as usable by champs with mobility. Now Ekko has four forms of mobility! What about AP tanks with strong initiations? Do you really think it's a good idea to let Nautilus spend 2750 on an item that lets him dash every 30s? Or Blitz? Or Amumu? Or Zac?

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I don't know if "lack of mobility" needs to be solved, but I do think that there either needs to be costs to mobility or answers to it for those who lack it, and my personal opinion is that LoL hasn't done a good job of putting appropriate costs on mobility in the last few years, and so I feel compelled to give champions that don't have burst mobility a few more of those answers to it.

I noticed that in your cass kit (which looked pretty cool!) but more directed at the hextech items, I'm wondering what the thought process behind them is

I assume they're designed to give immobile mages some answers to mobility to choose from (sustain, a slow, a dash that annie and malz will probably like, etc)

my questions are more like, what stops high mobility champs from also getting these items other than just not being worth the item space? and why pick the icy bolt item over a rylais? And why, slightly related cus its on the belt, put all the new CDR options on items that are situational but common, which makes it hard to plan out how much CDR you'll end up with?

ie my fav mid is Azir, and some games I buy zhonyas, some I buy abyssal, some I get both items and some I get neither. Often I don't know what items I'll be getting because it'll depend on who gets fed and becomes a threat to me. sorry I know this part is tangential and you're not even the item guy.

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I don't know if "lack of mobility" needs to be solved, but I do think that there either needs to be costs to mobility or answers to it for those who lack it, and my personal opinion is that LoL hasn't done a good job of putting appropriate costs on mobility in the last few years, and so I feel compelled to give champions that don't have burst mobility a few more of those answers to it.

I think one critical question to answer is whether more mobility gives diminishing or increasing returns.

If mobility gives diminishing returns, then less-mobile Champions gain more from these items

If giving a Champion +1 blink has diminishing returns, then I think creating broader access to mobility (through items, spells, etc.) is an effective way to "nerf" hyper-mobile Champions without actually taking away mobility those Champions are built around. In a "diminishing returns" model, your first flash gives tons of extra power, your next flash gives you somewhat less additional power, and so on. This might the case because, for instance, a match contains a sequence of "flash opportunities" that can be "purchased" by using a flash, and people who play smart will naturally tend to reserve their flash for the highest-value opportunities; additional flashes, then, simply let you buy second-best options, and third-best options, and so on. For example, let's say there are three opportunities: (1) Flash-baron-steal-ace (2) strong teamfight initiation (3) escaping a gank. A hyper-mobile Champion with two blinks might use the rocket belt to also pick up the third option, a moderate gain. But an immobile Champion with only one blink to start with would pick up the second option, a significant gain.

If mobility gives increasing returns, then more-mobile Champions gain more from these items

If giving a Champion +1 blink has increasing returns, then it's quite the opposite, as already-mobile Champions will gain more from these items than their less-mobile peers. An increasing returns situation would be one where, e.g., you can do awesome things with two flashes used in sequence that you could never do with just one, and thus a Champion going from one flash to two flashes gains more power than another Champion who goes from zero flashes to one flash.

In a diminishing-returns scenario, this item might be a good way to help less-mobile Champions

My intuition is that, on most Champions and in most circumstances, mobility has diminishing returns, so I'm tentatively for something like the rocket belt. I say "tentatively" because, as you yourself are obviously fully aware, it could have all kinds of unforeseen, complex outcomes. (Cue Jeff Goldblum.)

Concluding note: the PBE is (in part) for wild and crazy experimentation, so why not try it?

But I'm unambiguously in favor of trying it, at least on PBE. Isn't this part of what PBE is for? Getting large-volume, rapid feedback on sometimes quite revolutionary proposed changes. Sometimes I almost feel like Riot should distinguish between PBE updates, e.g., as "first-run" versus "pre-release". With the former being "hey let's see what happens" initial changes, and the latter being "okay, we're pretty sure we want this on live, so we're just running it through PBE for bug checks and stuff" revisions. That way, people might not freak out so much when they see "first-run" changes that give Tryndamere an AoE knockup ultimate and retcon Amumu's lore to a story about a trick-or-treater cursed to wear his bad mummy costume forever.

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I don't know if "lack of mobility" needs to be solved, but I do think that there either needs to be costs to mobility or answers to it for those who lack it, and my personal opinion is that LoL hasn't done a good job of putting appropriate costs on mobility in the last few years, and so I feel compelled to give champions that don't have burst mobility a few more of those answers to it.

Thing is for YEARS people have been saying that Riot doesn't give an appropriate cost to mobility. I think that's why his ...yes very hyperbolic... criticism hits home for so many people.

you could work on fixing the ultra high mobility, high damage, no mana cost champs.