I think the idea of a dark saber or beskar staff (any sort of Lore accurate melee really) would be a good step in the right direction, realistically the Imps only other melee is loosely the SBD. I don't mean to hijack your thread but I've put some thought into reasonable changes to Mandalorians that would make them the well rounded fighters that ARCs are.
Ultimately I think Mandos need a rework, IMO it's foolish they have to pay for armor. It should be 100 by default. Cut the jetpack that's found organically to the class and make it purchasable. With the points that remain from no armor investment and no jetpack it can get put into:
1) Having to buy the jetpack. (which I know would result in needing some models to be changed if they opt out of getting one, which could be a massive undertaking unless the models already exist), Fuel still staying the same but the jetpack costing a considerable amount. This change would make the class a bit more modular, the jetpack is a great asset but on some maps and in certain instances it can be more or less useless.
2) Dexterity in combination with Stamina, this would work because they would have no need to fuel thus those points can get thrown at either more Dex or Stam. This would also compliment the implementation of a melee weapon for this class. Making them more more mobile and not stuck to the floor after getting force pushed 10 times. And as mentioned prior by Maren, it could help circumvent them not being able to use their melee weapon with a jetpack they would be otherwise stuck with.
3) Beskar'gam, pretty self explanatory. For a hefty amount of points having this upgrade would provide reduction from all froms of damage (besides explosives, pulse grenades, fire, and poison from those careless bounty hunters) it could essentially be a sort of "cortosis" found on SBDs that would help a great deal in fights against Jedi. Being able to tank a couple hits from the medium styles at the cost of potential mobility, gadgets, higher tier weapons, and ammo would make Mandalorians more than just jetpack gunners.
4) Melee weapons; the dark saber, a beskar staff, vibroswords, etc... Perhaps make them each unique in their own rights, inflicting different amounts of damage at the cost of one weapon having a higher price point than the other. Or just kinda blanket them and keep them all the same after being added. It could also be limited to just 1 tier of saber defense if the devs are generous enough. Without the saber defense missing one PB block could mean death without beskar.
Sides note - I think gadgets should stay the same, maybe even add one more idk. Obviously the flamethrower would require fuel but not necessarily a jetpack. Could be limited to 1 fuel without said jetpack. Giving Mandos more ranged weapons would be a blessing too but not totally needed. Could range from the Westar 35 carbine (acting like a DC15a) to a slug thrower (a shotgun or maybe even a slow firing semi auto projectile rifle of some sort, obviously with decreased damage).
Just my two cents, I know its a big ask and the Developers of this mod have already put more than their fair share of labor into making the best SW game on the market, but any sort of change would be interesting to see. Hope this input is somewhat reasonable without going over any boundaries. Anyways, if you have made it to the end of my spiel have a good day and watch those wrist rockets.