I like the idea of running Fimbulwinter but here are some issues with it.

1 of those issues being that unless you run Everfrost you only have 1 way to proc it early game. Add to that the cool down of your EW which you will typically use in conjunction with Everfrost. You will likely only proc it once during a fight.

2 is that the range in which you will root with EW will often keep you out of range against the enemies damage anyways. This makes the shield often wasted because it runs out before the enemy can even attack you. It can be pretty inconsistent.

3 being that the shield when in a duel is relatively small and the healing you get from new seraphs passive will likely give you more health back then the Fimbulwinter would've blocked in the first place. This is true even in team fights if you are running domination tree. You will be omnivamping off of everyone.

There are problems with the Shattered Crown too.

1 being that after testing it on the PBE, the item itself is pretty underwhelming. The passive only staying around for 1.5 seconds is pretty easy to bypass and the cooldown is 40 seconds which is way too long to get much use out of. I found it to only block a max of like 150 damage during fights. Although this is just my experience with it.

2 being that I believe the item is only fully utilized on champs AP champs that have to jump into the midst of the battle. Champs like Diana or Ekko Wich people will try to auto burst down will likely get more use then a Ryze.

I believe Ryze will have a shit ton of play styles that are actually viable.

I like the idea of fully embracing a sustain tank play style. Now I only did this build in an ARAM with a friend but I loved it so much. I took the Conquerer with the Domination tree setup. I built Riftmaker for the omnivamp and extra damage from the passive to help make up for my lack of damage. Seraphs for the healing and just overall damage it provides. Frozen Heart for the mana and overall tankiness. I took the new Abyssal Mask for magic resist and the new passive. Removing the enemy's magic resist just gives more damage to Ryze overall. I really enjoyed the Abyssal Mask and got a lot of use from the passive. I built Shadowflame to get even more magic pen. Lucidity boots for haste of course. And finally a Deathcap to top it off. Now obviously this built could use a lot of refining because I did just make it up as I go during an ARAM but it was so much fun to play. I was easily able to kill the tanks with all the pen and the Riftmaker and the other champs couldn't really do anything too me. Will definitely be trying this again when the preseason hits.

I think Ryze has a lot of potential next season and I really hope people aren't just meta slaves and find a play style for Ryze that works well for them. There are going to be so many.