Is there an updated AIHostAdapter plugin that can pass new macOS notarization?

My company provides a solution that installs, among other things, an Illustrator Extension.  This Extension relies on the AIHostAdapter plug-in to get host events from Illustrator, and so it includes this plug-in as part of our installed files.

We are working on getting our software to pass all of Apple's new notarization requirements, and some of the warnings (soon to be errors) are caused by issues with this AIHostAdapter plug-in.  The plug-in we have is the same that was introduced with Illustrator CC 2014.  It still works as of AI 2020, but it will need updates to pass notarization checks.  

The biggest issue is that the AIHostAdapter plug-in is built against a pre- macOS 10.9 SDK.  There are also warnings that it is not signed and does not include a timestamp.

As a test, I created a zip file of the plug-in and submitted it for notarization.

At first, I get these errors about it not being signed:

"issues": [
  {
    "severity": "error",
    "code": null,
    "path": "AIHostAdapter_4.0_MacOSX.zip/AIHostAdapter.aip/Contents/MacOS/AIHostAdapter",
    "message": "The binary is not signed.",
    "docUrl": null,
    "architecture": "x86_64"
  },
  {
    "severity": "error",
    "code": null,
    "path": "AIHostAdapter_4.0_MacOSX.zip/AIHostAdapter.aip/Contents/MacOS/AIHostAdapter",
    "message": "The signature does not include a secure timestamp.",
    "docUrl": null,
    "architecture": "x86_64"
  }
]

It was easy enough to re-sign it with our Apple Developer ID, satisfying the above requirements, but the next notarization submission returned the following issue:

"issues": [
  {
    "severity": "warning",
    "code": null,
    "path":    "AIhostAdapter_4.0_NewZip.zip/AIHostAdapter.aip/Contents/MacOS/AIHostAdapter",
    "message": "The binary uses an SDK older than the 10.9 SDK.",
    "docUrl": null,
    "architecture": "x86_64"
  }
]

Fixing this issue obviously involves re-building the AIHostAdapter plug-in for macOS against a 10.9 or later SDK. Is this something that has been, or can be done? Has anyone else encountered or had to deal with this?

Is the AIHostAdapter plug-in still an officially supported thing?  Since the transition to the CEP platform and away from the Flex/ExtensionBuilder stuff I haven't been able to find any kind of official distribution channel for it.  

Thanks