Literally, any packages
I have written for the Molajo Framework the Joomla Framework can have if it helps you with your goals.
As a first suggestion, I would suggest the Fieldhandler
package which handles data validation, filtering, and escaping. It should be pretty easy to replace JInput with the Fieldhandler by adding a bridge between the two in the application layer (meaning the CMS). The benefits are that the various filters are implemented as adapters. It's easy to add new adapters. You can chain filters, etc., it's a step forward, IMO, from the current approach and something that could be implemented in a BC way in the CMS.
I would help implement that if there is interest.
Another package you might find interesting is Molajito
as a JDoc replacement. If you download it, run composer install, and point an Apache site to this folder https://github.com/Molajo/Molajito/tree/master/.dev/Sample/Public to see an example of it using files as input -- like Jekyll. I use it with Molajo but it's open for any PHP app. I changed the Interface
to match Michael's so it should also work with his Render package. I have a similar Render package in that Molajo can also use various rendering interfaces.
There is also an Event Package that integrates with the Plugin structure that's useful. If you find the FrontController helpful, I'm happy to share it.
I'm hooking tests back up for the Fieldhandler -- they are all in place but disconnected due to the Interface moving to CommonApi repository. It's pretty close -- if not already at 100% coverage.
PS - what the heck are you doing w Weblinks? Forget about it! The framework. THE FRAMEWORK! ;-)
PSS - please don't feel any need to respond to my off-topic rambling in the sentence above. I read and appreciate Micheal's statements on the question. (BUT FOCUS ON THE FRAMEWORK! ;-) )