And right there is why this suggestion is problematic for several reasons:
No active license - you realize you are putting you and your user's data at risk by not maintaining the latest version of the IPS software? I would be very surprised if you are patching bugs and keeping up with changes to PHP versions, etc.
While plugins and apps are useful, unless they are maintained and managed via IPS and the developers you run the risk of breaking your community software if an addon doesn't keep up with any changes to the main suite (and any bugs)
Using unsupported apps outside of IPS again underscores the above risks, and potentially opens you up to liability if someone decides it is your fault, and not some developer you hired to create an addon that has leaked their personal data or made it vulnerable to exposure.