[Victorious Razor]

The normal random plant spawns that aren't reliable enough to make a 9* worth it, as the chances of always having flowers spawn in places isn't that great, especially since there isn't a way for you to have control over moving it.
Summoning a plant just to turn it into ice and have it explode can run 7m, which makes it arguably one of the worst combinations you could probably do as there are many other maneuvers you could perform for more damage/better effects, making it pale compare to Yukijin.
Just to compare, I can sidecut and sheathe sword, which would do more damage (and a better variety of damage) than the proposed combination, and even have the chance of gaining 3M back if my sidecut crits.
1m to summon the plant, 3m to turn it into ice, 3m to shatter it and deal some damage and maybe apply frostbite. Frostbite won't be that useful due to the number of abilities that allow you to move without triggering the ice tiles, or even deal damage without needing to move in the first place.
If creating ice statues with Sogensara cost 1m, and didn't need specific targets but could only be used once per round, I'd be more on board.

However, I think a good baseline idea is if you have to play a specific race and, really, only that race to make the potential of a weapon worth using, then it's a bad idea for a potential.

Another idea I came across, however, could be based on Frostbite.
Sogensara, say, gained damage (flat) based on the amount of Frostbite on the target, and maybe the ice damage has a status inflict chance to give the target Frostbite, and the lvl of Frostbite was able to be increased based on a % of damage dealt by the weapon. It'd be, say, 10% of the damage you deal would be the added lvl of Frostbite, with the duration refreshing if it's actually applied.
That'd be another way to make the potential worth it.