We are developing a basic back-end app where people can admin their News, Events, Home Page Highlights, etc... The problem arrives on the following scenario:

The client (a nursery garden for example) tell us: Beside News, Events, etc... I wish to also manage the Plants of this specific type unique on our Nursery Garden.
Of course we can well create a model for that on the back-office but, if we do so:

Issue 1) we have trash our application with some specific stuff that will, almost certainly, not be used by anyone else besides this client;

Issue 2) If 100 more clients arrive requesting 3 or 6 specific pages to be administrated, this trash get's event worst.

Can I please request what could be, on your opinion, a proper design pattern to apply here ?

Thanks in advance