If she's using her power to their maximum extent, it's unlikely that they'd involve flowers at all. She'd just shoot lasers and stuff, because that's something anyone can do. The wording of their powers is an intentionally vague "to the extent of manipulating X", which implies that they can do things other than manipulating X. Which should be obvious since they can also shoot lasers and fly and whatnot. Yuuka isn't limited to flowers, it's just something she chooses to do for her own reasons. So I think your idea is flawed from its premise.
Well, of course i'm not limiting them to simply use their abilities, but anyone can write about fights with humongous lasers, magical blasts and uberpowerful punches (lol that sound like Dragonball
).
It's when they decide to use their abilities that i'm trying to be accurate, because it's the real tricky part (and some of them can practically use ONLY their abilities, i.e. Medicine.... apart from her poisons she only have regular danmakus, which are almost useless in a real fight)
If we think about it, half of them possess game-breaking or outright OHKO abilities, so merely using them would turn into a quick-draw contest.... and since they are used to fight with danmakus, where one of the points is showing off, i think they would really crank up the power only when pissed off.....
Trust me, i'm trying to throw as many curve balls as possible with the fights, to make them interesting.... heck, i've found a perfectly canon way to make the
AKI SISTERS's abilities useful! (and i'm quite proud of it :V)
And yes, Yuugi is a badass..... but since we are speaking about Gensokyo i think almost the entire cast qualifies :]
EDIT: since i'm at it.... taken from the wiki's page about God: "Of note is that loss of faith for a god means a loss of their ability to manifest their power. For a god, losing all their power is equivalent to death (with the exception of arahitogami, who would continue to exist as normal humans)."
Does that mean that they literally disappear/die or that they become something like a simple divine spirit, powerless and unable to express themself in the physical world?