Selecting any personality other than "Nymphomaniac" will lock the Juicing skill, so the only way to go for a mix build between physical, magic and juicing is to select no personality, but selecting no personality will leave you with very minimal DEF which will easily hit the zero if injured. I don't think it's a good idea to spread your trait points across COM (physical), WIS (magic) and CON (juicing), your damage and endurance will both severely suffer. You will not suffer a bit, you will suffer A LOT, to the point that the challenge won't even be fun. It's best to specialize yourself into one thing, if you wanna do physical damage, then put most points into COM, if you wanna do magic damage, then put most points into WIS, if you wanna juice, then put most points into CON (or COM if Bloodlust is enabled, still can go CON even if Bloodlust is enabled). So yeah, unless you cheat and put max points into every single trait, a build between all 3 classes isn't really viable, especially early game.