As you probably know, there's almost never just one solution to a problem in MODX.
One way might be to leave the TVs, but not use them for the display. The values could be written to a custom DB table when the resource was saved in a plugin attached to OnDocFormSave. The technique for creating the custom table is described here:
https://bobsguides.com/custom-db-tables.html.
The article doesn't use a plugin, but rather a regular HTML form, but once the table exists, the plugin could write the data if you want the users to continue using the TVs -- or you could move to using a page with the form.
Another way to go would be to extend the modResource object with
ClassExtender and use the snippet that comes with it to set the placeholders. The fields would appear as extra input fields on the Create/Edit Resource panel rather than TVs.
Another option would be to use MIGX. I don't have a lot of experience with it, but people love it.
Since there aren't that many of them, you could also create a System Setting for each field, use ClientConfig, or a custom form, to let users update them, and display them with System Setting tags:
That should be quite fast, since System Settings are automatically loaded on each request. The down side is that it would slow down loading of all the site's pages, though probably not by a noticeable amount (most likely a few milliseconds).
