Pricing goes through sales. The operational half you are worried about is already settled, which should make that conversation a lot shorter.
On key ownership, a rollout your size would be a single key with multiple activations, and the key belongs to the account it is activated under rather than to a person. The thing to get right on day one is the email address, because the first activation ties the key to that address permanently. Use a generic one, [email protected] or similar, not a named admin.
Activating a company key under someone's work address is exactly the failure you are anticipating, and it is unpleasant to unwind after they have gone.
On reimaging, the image has to be unactivated and activation happens on the destination machine. Pre-activating into a golden image does not survive, the license.sig it writes under ProgramData gets overwritten by the deployment.
A reimage only counts twice if the old activation is never released. Deactivating before you wipe frees the seat, and when a machine is gone before anyone thought about it you can release that activation from the account page instead.
On deployment, it goes out through what you already run. The installer takes /s, plus /noreboot if you are controlling restarts, and activation is a separate command line step after it.
Three things that catch people on the first wave. The activation window and the app UI still open after a silent install, so the script needs a taskkill between the install and the activation step. The installer returns 9 for a successful upgrade, so set your tool to treat 0 and 9 both as success or every upgrade will report as failed. And the activation command wants -company="Stardock" literally, not your company name, which is the single most common reason a scripted activation fails.
On the part you said you would pay extra for, the licence state is a file. A successful activation writes license.sig into ProgramData\Stardock under the product name, and that is what Intune detection rules key on, so your tooling can report activation status across the estate without anyone touching a desk.