Okay, here are the scripts. First up, switching weapon sprites based on the loaded ammunition. I've attached the mod I made for Ivan using his sprites to make the RPG in Piratez change its sprite when a Baby Nuke is loaded - this provides a good example of how the script works. In your mod, you'll only need to copy over the file weaponSpriteBasedOnAmmoScript.rul, and then follow the example in the other ruleset file for each weapon/ammo combination you want to set up. In the weapon ruleset definition, you just need the extra tag ALLOW_AMMO_TO_RESPRITE: 1 to enable the new feature in the script, then use the tags in the ammo item (NEW_BIGOB_FOR_WEAPON: <some number>, NEW_FLOOROB_FOR_WEAPON: <some number>, NEW_HANDOB_FOR_WEAPON: <some number>, and CURRENT_MOD_OFFSET: current) to pass the new sprite numbers back to the weapon. Unfortunately this means that sharing ammo between two weapons that have this feature activated will cause them both to use the same set of sprites - this is a limitation of how I implemented the sprite switching, focused on making the ruleset as simple as possible.
As for the personal energy shields, I put together a sample ruleset for SuperCaffeineDude a little while back, if you just want to add it to armor definitions, that is available
in this thread, with a short explanation of how to use it. To have it work for the aliens as well, all you need to do is add the proper tags to their armor definitions.
If you want a more complete set of scripts for various other defensive options including having energy shields as a held item, look for the file YankesScripts.rul in the Piratez download. It contains the armor-based energy shields I sent to SuperCaffeineDude as well as a few other things I've written, some of which are implemented in Piratez.