
Luftwaffe Ju 52s dropping paratroops

Internal view of Ju 52 showing a beam defensive MG 15 gun and ammunition racks

Now this goes along with how we currently transport troops (albeit in an alternate universe).
Junkers C-79, s/n 42-52883, at Howard Field, Panama Canal Zone, late 1942 with the USAAF 20th Transportation Squadron, Sixth Air Force.
Historical correctness aside, the addition of 1-3 machine guns in rifle caliber would not change much in terms of survivability. The only thing you could reasonably hope for is getting a ping on the fighter before he augers, so that you would finally some perks for that.
But it still would be a sitting duck. A Ju-52 even more so. It would see very little use outside of scenarios.
Although I agree with Snailman's assessment, I still give a

and could you imagine if:
Half-track motorcycles (kettenkraftrad) and parachute troops' supply canisters were secured under the fuselage at the bomb bay exits and were dropped with four parachutes.