I don't think it would be difficult at all to switch to bootstrap-vue. What the -card components do is wrap the raw component in a v-card and add a v-card-title inside of that, etc, to position everything. So it's really "just" a matter of changing some tag and class names to use comparable bootstrap-vue functionality. (Plus spend hours tweaking the CSS crap...)
I don't think it makes sense to "reproduce a card without a dependency" because the whole point of bootstrap-vue or vuetify is to get a uniform look that can be customized easily. So while you can, of course, produce something that looks like a vuetify v-card using a bunch of div's and styles I fail to see the point because if you'd load those into a bootstrap-vue project, for example, these things won't look like the custom cards/widgets you craft in for the rest of the page.
