I'm curious because I really don't wanna depend on companions

Yep. Easily.

Not really difficult, just make sure you create a tough character. Reasonably high Endurance and a high Agility help a lot. You'll probably need at least two tags on weapon skills and a high Intelligence to get the skillpoints needed to enhance your weapon skills fast. You can drop Charisma to a minimum since you don't need it for getting companions, but that means convincing people to avoid combat is going to get a lot harder.

It borders on impossible to beat Fallout 2 with companions who are still alive. (aside from leaving them in safe places when you go do dangerous things)

The final area involves you going alone, so yes, it can be done. Mind you, the final fight gives you a set of companions and some mechanical assistance if you're clever enough. Its your choice to take advantage of them, but but I sincerely suggest you do so because the final boss will otherwise tear you in half.

Yes, I completed FO2 as a solo sniper numerous of times.

If I put Charisma down to 1 what would I lose out on

Charisma is useful for keeping your dialog options open although you can pimp your speech skills, charisma is not nearly so important as Intelligence. It determents the maximum number of followers and is equal to your CH divided by two. Even if you don't plan to keep any company you might want to set it to 2 so you can at least pick up NPCs temporarily for xp, carry stuff and such. It can be increased by 3 points during the game by gaining the charisma perk, surgery and with a specific item. It can also be decreased by certain special perks.

Another thing is that you cannot get certain perks, but that goes for all stats. See perks list at (minor spoilers): http://fallout.wikia.com/wiki/Fallout_2_perks

And you cannot sleep with certain npc's in Modoc and New Reno, if I remember correctly which has its advantages and disadvantages.

That's all I know the rest you'll have to look up in wiki or Per's walkthrough.

I finished it with a melee character without companions easily. I think it's easier without them, if i use them they are just mules.

You can take human companions in power armour... Or at least it worked for me. You can leave everyone else near where the final battle will be and use them in the final battle.

Umm, no. You're thinking of Fallout. In Fallout 2 you'll have to reload way less to keep them alive (because they can wear armour, even Power Armour). Still, I leave them behind for the last mission, so you're kind of right. They still make most of the game easier.

Umm, no. Im thinking of Fallout 2. Please dont presume my thoughts.
You're very unlikely to have your group of companions intact at the very end of the game. Im not kind of right, its exactly what ive said. It does become almost impossible to keep them alive unless you hide them away/ continually reload, as you have just admitted you do.

I never have any major problems keeping my human companions alive, and regularly take Cassidy, Sulik and Vic through the entire Rig. I ensure they have at least 6 stims on them at all times (and are set to use them), ensure they are well equiped, have a high Dr skill (to get XP from their injuries) and ensure they are well rested before continuing after a random encounter.

I don't ever try to protect them by having them wait, I just order them to stay close and don't scrimp with the Superstims when they hit 33% of HP.

In short, I think you're wrong.