I'm open to suggestions but I think the best solution would be to add a field to the website module.
from odoo import models, fields
class WebsiteInherited(models.Model)
_inherit = 'website'
no_footer = fields.Boolean(string='Website Footer', default=False)
Then create an xpath to the footer
<template id="footer_custom" inherit_id="website.footer_custom" name="Footer">
<xpath expr="//div[@id='footer']" position="attributes">
<attribute name="t-if">not request.website_id.no_footer</attribute>
</xpath>
</template>
Untested but I assume something like that.
Edit:
I forgot to mention you'll have to add the no_footer to the website view so you'll be able to change the value