"New weapons for the Vengeance" seems to be one of those things the VFX folks very much did bring to the Trek universe, without requiring writer prompting for that. Phaser bolts that curve madly were supposed to be a cool way of portraying warp exchanges of phaser fire, but JJ Abrams liked those so much that he wanted them in the lunar standstill fight, too. We got to see the detachable fighting drone as well, even if only briefly, and an atypical turreted weapon was prominent. None of that made a difference in plot terms, but they added to the plot by giving the black hat ship a flavor of her own.
"Writers imagining it" is not much of a requirement otherwise, either. The transporter came to be because of budgetary issues. Intriguing revelations about mystery characters like Spock or Data were made possible because the writers originally refrained from doing any imagining, leaving the sandbox covers off for the next bunch of kids. And actors have input on the characters that sometimes makes all the difference even when not appearing to make any originally (never pinches, say). Not to mention they have output: they are the characters and the story, and they are the ultimate judges of the fictional universe. Anything caught in their filters fails to become part of that universe; anything given a specific hue when going through those filters remains that hue, rather than any the writers might originally have intended. The same with VFX, set design, costuming: unless the writers perform a last-minute intervention (and they never do), input/output from those sets of professionals supersedes writer intent.
So far, ship VFX in DIS has been pure set dressing, with no plot implications. We haven't even seen any 32nd century ships in real action, demonstrating 32nd century ideas and practices (those Earth guardians perhaps notwithstanding, and the flavorless chase scene with Voyager-J in the lead very much withstanding). The first inkling of ship design that might matter, and might have character, would be the Voy-J having this new drive system that in theory could be plot-relevant in a way the fancy detached nacelles really aren't. And then there's the upcoming Discovery-but-not-quite ship that probably is plot-relevant and might be spore-driven, and her recognizable shape would then very much be another case of the VFX artists participating in telling the story. But we'll see.
Timo Saloniemi