Constructed Pugilist Jistkan Artificier

As the title suggests I'm considering playing a multiclass of both. This isn't under Rules since I'm not asking if it's RAW. How would you play them. Both offer similiar and different options for the arm. Would you allow them to function on one arm itself or have both arms be artificial. Under Brawler the arm suggests it is more like a glove you slip on while under the Artificier it says an arm is grafted on suggesting it replaces the arm itself. Is this even worth really doing? Probably not. Caster classes are meant to be single class or Prestige Class where casting abilities continue.
Would I allow it to be combined into one arm? Yes. Think it would be cool. Grappling Hook with magical features added. Extended arm with Piercing Keen feature.

Mechanically I can't see anything that says they have to be the same arm, or that they can't be. Thematically makeing them the same arm seems more fun to me.

There are some abilities that won't stack - eg. The Shielding Limb from Brawler and the Shielding Arm from Magus won't stack, so there's no point in taking both. Likewise you wouldn't stack enhancement bonuses on the arm (although the Arcane Pool enhancement will stack).

Honestly, it's probably not the strongest character, but it'll be thematic. My take would be to take a single level of Brawler for an interesting limb modification and the rest in Magus, but no pressure.

It'd probably work out alright to allow the person to keep the golem arm for upgrade and replacement rules, and just apply the constructed pugilist modifications on top of that. If someone was trying to do this at my table, I'd let them combine the arms, or make each arm the golem type arm since I'm not sure exactly how functional the prosthetic is meant to be.

It sounds like the prosthesis is meant to allow a tentacle or something to function more like a hand, but I'm not really sure.

I have looked at both classes and Brawler only offers a couple of enhancements I like so I'd be taking it only until I get them the rest would be Magus. It always seemed to me that both classes would work well together.
The idea of one arm itself came from a picture of a pegleg hooked hand pirate. The Hook would be more functional then a simple hook. Grappling piercing damage. Etc etc. Just wondered if people thought.

I was looking at doing this combination myself. For me the brawler doesn't offer as much as the magus in regards to the arm stuff... but it does have a couple things....

For me i would take just 2 lvls of brawler, for the shielded arm and the free feat. The brawlers version of shielded arm does not have the hindering effect that the magus version had..

Shielding Limb: The constructed pugilist learns to block blows with her mechanical limb. She gains a +2 shield bonus to AC, though she loses this bonus anytime she loses her Dexterity bonus to AC.

Vs the magus....

Shielding Arm (Ex): A Jistkan artificer learns to deflect blows with his arm. If he is not wielding any other weapons, he gains a shield bonus to his AC equal to his golem arm’s enhancement bonus.

So a flat +2 shield bonus all the time. Then i would go up the rest of the way in magus. I know multiclassing a spellcaster is serious taboo to most people but if i was doign this combo, thats how i would go

Are you likely to be wielding other weapons?

If not the Magus Arcana can get you up to a +5 Shield bonus to your AC (possibly +7 with Bane Blade at level 15 ... not exactly sure how that works).

Probably go with 2 weapon fighter build. Use artificial hook hand with cutluss or heavy pick shaped like an anchor. Pirate themed campaign if things work out.