I want to quit Andromeda Initiative. It's a suicide mission.

What does that even mean? If it has one weapon, that's its main gun, by default.

I don't expect it to have a Thanix cannon as that may not have been available by the time they left. But for fuck's sake, it better have something.

It has a pistol in the glovebox.

I think people are thinking that the Pathfinder is just Shep in Andromeda. What everyone is forgetting is that Shep was an N7 Alliance Marine and a Spectre. He was tasked to engage in combat to stop threats to Council Space and the Alliance. That's why he is in command of a weaponized frigate with a tank. The Pathfinder is not the head of a "strike team". He or she is supposed to find a new home for humanity, not destroy all the enemies! What the Pathfinder actually ends up doing as our PC will probably be different, but we don't actually know if the AI has a military strike force to supplement the exploration teams. Lewis and Clark did not take a Gatling gun with them on their expedition. The Pathfinders are not military units.

I bet 100% if there is any danger for your life you will sell your soul to everyone, who will give you one minigun instead of drones  

Sure; but did you get the reference?

But that's not it's purpose.  And with the biotics, flamethrowers, and other weapons carried by the crew mates on board, I think we'll be fine.  It's not like I'm toting my violin in there.

Regarding number 1. You/we don't know how much mass is located behind staircase. All that is required is for it to be greater (not just equal, because things move around inside) than the mass in front.

So long as the centre of gravity is safely behind the bottom of the staircase or in front of the rear gear, the ship will not tip forward or backward respectively. The staircase-ground contact is around located about 50-55% of the total craft length behind the nose, and the rear gear are at about 75-80% back from the nose. If you just had the stairwell contacting the ground, it's clearly obvious to me the ship would tip back not forward. With the rear gear there is no chance of the ship tipping forward unless you somehow managed to shift most of the weight to be in front of the staircase.

In fact, look at these images



Notice how the rear landing gear isn't actually in the rear half of the aircraft? But your aircraft don't tend to tip backwards on the ground (so long as the ground crew remember procedure. If you load the fuel, passengers and baggage in the wrong way, it can tip) On this A320-200, the rear landing gear is located 17.37m from the nose. The total aircraft length is 37.57m. In other words, the real gear bogeys are located at a point ~47% of the length behind the nose.

TL:DR This isn't a problem.   The landing gear do not need to be at the either ends of the aircraft for it to be ground stable (actually, you usually explicitly don't want this in aircraft).

Some extra thoughts:

For most modern aircraft (civil or military), the engine weight as a ratio of the maximum take off weight is somewhere between 7 and 10%. Don't forget the weight of reactor and/or fuel which is clearly for the Tempest going to be concentrated at the rear. For most civil jets, we're talking somewhere in the region of a 35% ratio between the maximum fuel capacity and the total aircraft weight. Given the shape of the Tempest, it's likely the vast majority (70%+) of this is in the rear. So we're at 35% of the total weight being behind of the stairwell with just the fuel and the engines.

EDIT Furthermore.  This is the Boeing 727



It looks like it should be back heavy (it is), but it's not tipping backwards because they put the rear gear behind the centre of gravity

Source: I have a masters degree in aeronautical engineering.

Also, all we know about the Tempest's weapons is that the ship doesn't have a main gun. This is not the same as "this ship doesn't have guns". The Kodiak has lasers and missile launchers. I think it's fair to expect that something along these lines will be present on the Tempest. The Nomad is unarmed. 

Of course Lewis and Clark didn't bring a Gatling gun on their expedition. Their expedition was from 1804 to 1806. The Gatling gun wasn't invented until 1861. 

Noone tells about heavy weapons, nuke bombs or rocket artillery! Two stationary automatic machineguns are not so heavy to make the Nomad slow. But as oppressive fire or in case of Nomad damage they will SAVE YOUR LIFE!!!

Guys, there is LETHAL DANGER OUTSIDE! And you don't want to take machineguns with you?

The Darwin Award 2017 is yours!

Pff, you do know that you can go out and kill them? But don't worry, you are not going anyway.

And if it is that easy to get a Darwin award, every fucking scout and recon unit in the world will get one.

Maybe a bad example, but isn't the USS Enterprise from Star Trek build for exploration as well and not for military purpose?

Yet that ship has a shitload of weapons. Ofcourse no stealth system, but still.

Going into a new galaxy, where there are obviously going to be hostile races, without any defences on a ship is simply suicide.

From what I can tell, the Diagram also doesn't show landing gear.     Guess we won't be able to land then.

If the captain is on the ground and there is an enemy in space then several things could happen:  
1.  The enemy is large enough that the weapons on our SCOUT SHIP wouldn't be able to destroy it anyway, and thus the point is moot.  However, in this case because we have a small ship that can enter atmosphere and most large ships cannot, we just fly down and pick the captain up.
2.  The enemy ship is the same size as ours.  Well, a firefight between two matched opponents doesn't guarantee our success, so we might die anyway.  Better to go to FTL where we can't be tracked, move slightly around the planet, fly into atmo and pick up our captain.
3.  Ship is much smaller than ours (think x-wing) and is shooting at us.  Well if it's that small our shields should hold, unless it has super-lasers.  In that case, please refer to option 2.

As for the other scenarios, remember that it is a scout ship.  The size of weapons on it would be small, and thus ineffective against a lot of enemies. If protocol for the AI is to run at a sign of trouble, there shouldn't be any need to rescue another ship.  If they do get caught, it's probably by a larger ship where the weapons wouldn't be effective.  There could be a circumstance in which it could be useful, but at that point you are talking about not wearing your seatbelt because 1% of the time in a car crash it can cause serious injury instead of saving your life.  It's just not practical for what the Pathfinder's job is.