OK, I think in terms of balance there is lots to discuss.
So I will comment on your ideas and also present some of mine

.
Only important thing to know is: so far I've played only on Easy and have not Unlocked/Played the slug and mentis cruisers.
Personally I like the Idea that you can see, that different enemies rely on different tactics. And the nature of tactics is, that they always have a counter tactic and also always counter an other tactic; simple and old rock-paper-scissors principle.
So especially in the beginning of the game your start equipment is not able to face every enemy ship as you are able to play only one tactic meaning that you will encounter ships that counter you and force you to jump away.
Unfortunately that is something I rarely experience!!!
Also the AI often is just stupid; not timing the use of their lasers or boarding really stupidly. Sometimes I think I could have still won the battle if we (the enemy and I) switched ships, just because the AI does not know how to use his setup. This leads to my first two points:
-Increase the rock-paper-scissors principle and make players really think about jumping away
-Improve the AI to frighten the player more! This also supports the above point.
Next we can face the 'boarding-advantage-problem':
This could well be solved by the above changes

but there is still more that could be done:
Make it a difference in terms of a choice and not an improvement.
*Boarding: less scrap but more valuables: fuel, missiles, drone-parts, chance of crew-member, chance of weapon(which in the end is scrap; often)
*Destroying: more scrap but less valuables; almost no chance of crew-member and low chance of weapon
Further boarding could made be more dangerous by Improving enemy ships a little bit (Doors, anti-personal-drones), and the AI trying to destroy the teleporter to prevent 'backporting'...
Or by adding a new defensive system that is made to prevent boarding and offers abilities like lockdown, or heal-bomb, or improved-combat-damage. I'm looking forward to 'the big Update' and how this works out.
So we are down to some points:
-Improve AI (Again)
-better equipped enemy ships
-New anti-boarding systems?
Another thing to consider is, that the today setting of ships perfectly supports boarding: you have four system that can be manned and so you have four members left that can be trained as boarders; is pairs or even as a group if you have the respective ship.
With the Update this will change as you may want to man more systems than you can with a eight-man-crew consisting of 2-4 boarders. This could further be supported by allowing multiple manning: e.g. you could man the weapons with two members both getting experience and increasing the recharge rate. Same for shields. Also allowing a manned cloak (cool down and evasion rate) or manned Drone-control (you can set priority targets and the drones will try to attack those) can make things more interesting.
So the points here are:
-More manned systems to prevent 'the perfect eight' crew.
Then there are some aspects about the races that I want to see changed/improved:
First I really like the crystals and the fact they have a special ability, so I thought of more special abilities for all the other races. But before I get to them some other little things.
I noticed, that there are two races I almost never use:
Humans and Slug.
SO I asked myself: why?
And the answer I fairly easy: Both do not offer anything really helpful.
Sure none of both have disadvantages, but most of the disadvantages of other races are easily outranked by their advantages and the right use of them.
So I felt like both of them need slight improvement.
For the humans my solution is very simple but I think brilliant:
Humans need less experience to complete every skill (e.g. to get combat rank-up the only need 6 instead of 8 kills)
Why Is this good? Well this way the still are 'weaker' then all the other races if compared to this races strength, but as the time in 'a fly-through' is limited making skills is an important part and can not always be reached.
For slugs I don't have a really good idea. I just feel the 'slug-sensors' are way to weak as the are not useful most of the time(even without sensors it's easy to deal with introducers (look on door movement and systems being attacked) and if you played for some time you know how many people are on enemy ships, and where they are).
So what about slugs reduce the attack speed of who ever they attack by maybe 10%
Other would be they reduce movement speed of enemies; either the whole room or just their 'pray'.
So here we have:
-Humans need less EXP to get lvl ups
-Slug get another light bonus
Getting to the special abilities of other races:
Zoltan: provides one additional energy for x seconds. (maybe 15?)
Engie: Can instantly repair a system. (1-3 points, maybe depending on the system); alternatively: repair-speed doubled
Rock: can negate ion damage or if there is no ion damage on the room they are in they become rocks for a few seconds; meaning they cant attack, but also cant take dmg (but still be attacked)
mentis: gain attack speed bonus
Human: gain an additional tier of every ability the have (goes up to t3) for a short period of time
slug: mentally control an enemy for a short time. (like the announced system for the update is able to)
crystal: as they already have an ability they need a 'passive' bonus, I thought of 10% less damage taken or 10% damage taken is reflected (they still take it but the enemy also does)
-improve diversity of all races
So far this are just some 'minor' ideas and suggestions I have.
Let me hear what you have to say

AkantorJojo