A mash up pack isn't for PC- they are for CONSOLE! Consoles don't have ANY of that! Listen, a mashup pack is literally only a pack of skins. Nothing more, nothing less.
Anyways, this wouldn't be impossible to do, but since this is suggesting a mash up pack, this should go into one of the console sections. If you wanted a resource pack, try asking for one in the resource pack section. Mojang won't ever make mash up packs for PC.
Yes I am completely aware that mahup packs are skin packs for console MC. But he stated that the MC: Story Mode's models and textures are impossible even though they are completely possible to make.