This is a simple voicepack with Commander Shepard's voice. This voicebank file replaces the voicebank for the male Pragmatic voice ingame. Installing this is extremely simple:

• If you have the game on Steam, go to :\Steam\steamapps\common\Pathfinder Kingmaker\Kingmaker_Data\StreamingAssets\Audio\GeneratedSoundBanks\Windows on your PC and simply pop this bad boy in there to replace the old voicebank. You might want to make a backup of the old file.
• If you have the game on GoG, go to :\GoG Games\Pathfinder Kingmaker\Kingmaker_Data\StreamingAssets\Audio\GeneratedSoundBanks\Windows and do the same as above.
  

After that, just select "Pragmatic" from the list of male voices in character creation and you're done! Your character is now voiced by Mark Meer.
You can also manually import a Shepard portrait included with the voicepack download for a full immersion!

This voicebank file is noticeably heavier than the original, with this being 20.1 MB and the original just 4.7 MB. I haven't noticed any loading issues caused by its size on my part. Hopefully it shouldn't impact anybody else either.

Huge thanks to MJpoland for letting me use the voiceclips from his XCOM voicepack. I literally couldn't find Shepard's voicelines anywhere else, and I uninstalled Mass Effect 1-3 from my PC a long time ago. Unfortunately I don't have a video to showcase this voicepack ingame at the moment, but you can check out MJ's pack for XCOM to get an idea.

I'll try to record a showcase (hopefully) in the near future.