this just replace the model and the base anims and the original animations doesn't have a walk animation, i think is impossible adding new animations and not replace the originals

i think you could get it to work if you accuire a qc file from one of the hl2dm or gmod 9 playermodels by decompiling them via crowbar, tweak some of the file paths in your playermodel qc so they match up with this model's file path, add the sequences from the initial playermodel, if needed rewrite the qc to include vehicle anims, use crowbar to decompile this model, replace the existing qc your modified qc, recompile, put the mod's vpk in the custom folder located within steamapps/common/Half-Life 2/hl2 and run the game. this would theoretically work, though differences in source sdk sp and mp may cause issues with the animations. this is a possible way to get it working, though it may require sourcemod to run custom scripts, overall, this is the most logical way you could animate it. this worked for me in mapbase so it should also work here.