Do you know about the fields-block plugin?
If you’re just trying to “show the fieldset as the preview”, this might already do what you want. 
If you instead just want to show one of the page fields in your block fieldset, you might be able to just pass the <k-pages-field> components all its props by getting them from the panel:
<k-pages-field v-bind="field('pages-field-name')" />
All block previews, when registered via:
panel.plugin('my/plugin', {
blocks: {
// here
}
})
Inherit some helper functions from the k-block-type component. One of that is the field(name, fallback) function which gives you the definition of a field in the block’s fieldset by name.
I haven’t actually tried the code above, but I think it could work.
Otherwise try to console.log the field('pages-field-name') return value and see if the props are somewhere in there.