Okay, this is going to be speculative - by neccessity since this is still very early days for the character and we likely won't know with any degree of accuracy until 2022 rolls around at least. Still:
On a top level I feel that he's going to be dependent on now just getting consistent Electrics but also mixing up the Crouch Dash options consistently and getting as much % as possible out of the openings he manages to get. How many openings he gets per stock is going to be very difficult to say right now, but if he only needs say 3-4 to KO someone on average he'll be extremely dangerous to approach.
Proto in the above linked video called Kazuya a "Muscular Luigi" (31:40) and I can def. see where he's going with that. Doesn't have many tools to play a long range game despite the intangible hitboxes and what not, but when he gets in ooh boy the damage racks up fast. Does have the aformentioned air problems, although his aerials are not shabby at all and can make it difficult to contest him... if he's anywhere close that is. Which does present a problem for Kazuya players where his opponents can choose a less commital option or space away from his aerials.
Of course, prominent zoners (not just
and
, but including them) are likely going to cause major issues for Kazuya - while top Kazuyas can and will often get by a lot of stuff with Crouch Dash's and his attacks' intangibility it only takes one or a couple projectiles to send the Kazuya back to neutral (not helped by the reflector kick having a lot of endlag making it rather impractical). Characters and players that are good at juggling will likewise pose a significant obstacle for him because that's one of the safer ways to rack up damage on him.
Still I do think Kazuya has the potential to have a good overall matchup spread - his disjoints and intangible moves make it very difficult to get up close for most of the cast, and maintaining a lead on him is going to be very difficult when most of his tilts do 15 %+ and he has combo starters out of the wazoo. While his normal stats are bad he does have the ability to close in due to the Crouch Dash. CD does also lead to three different attacks - giving it a lot more versatility than just the leadup to EWGF. Dragon Uppercut for example is a stupidly strong finisher even if it's hella commital.
As far as stages go I do think he's going to want stages with wider blastzones - he doesn't have any trouble killing and would like to survive for longer. As far as platforms go his players might think it's better to go for say Kalos than Battlefield, because Kalos' platforms are at the edge and allow some recovery mixups. Which might be a problem during a set since an opponent may choose to ban Kazuya's best stage or at least force one game in a Bo3 to be on a pretty bad stage for him. While this is something every character has to contend with it's particularily important for Kazuya due to the jumpsquat and general movement hindrances.
I do think that he'll also suffer a bit from the volatility problem akin to
: where the current double elimination system means that a truely bad MU or loss hurts a lot. Due to that and how technical he is not a lot of people will main him and he'll likely require secondaries for bad MUs, but Kazuya's coming into an ecosystem where most pros have 2-3 characters they switch around anyway, so I think he'll be fine. A pro like ESAM can decide to go mostly Pika or Min Min, then go Kazuya not only to help cover MUs they struggle a bit more in but also to catch the opponent off guard.
Overall, yeah he's likely to be quite polarizing and unlikely to be the tippy-top of top tier, but he's still a character to look out for.
