Of course of coruse. Its always better to start with the core features. Early polish is a bad idea. I know a laser sword is very similar to the katana in Karlson, however your modeling skills are quite good and having a lightsaber would be fun. Although it might be a good idea to stray away from anything more to do with Karlson and focus on a new direction with the 3d parkor genre.
This game is very similar to Karlson. I recomend adding a gimick that makes it stand out from Karlson, like interesting abilites or a more intersting map. Maybe a futuristic city, or a cyberpunk dystopia if you are feeling ambitious, however that might take too long.
The weapon models look very nice, if you made them yourself, you should add melee weapons, perhaps a laser sword or something.
