Like Doctopus pointed out, the "vanilla" game do have several balancing issues: Unplayable faction, for one, have limited and (often) weak blocks. When making all blocks available for a single faction, like Reassembler, this result in a lot of blocks being useless or so underpowered that anyone is unlikely to use them at all...

In designing this mod, it quickly became evident that only copying all blocks from all the factions would not result in something very interesting. I tried to maintain the flavor, so to speak, of the originals. Most block name were changed, however, for the sake of making things concise and accessible. You will likely recognize from which faction a particular block group was taken from rather easily, even with changed names.

So, to answer the question: Yes, a lot of blocks were rebalanced in several different ways:

A - Make them cost P so they are not available from the start.

B - In the case of Hull and Armor blocks, have each category have at least one advantage be it weight, resistance, regenrate or P cost.

C - For thrusters, rebalance was mostly focused on Thrust to Weight ratio, i.e. heavier/bigger thrusters in a group always have the same or better TWR than lighter ones. In vanilla Reassembly, this was not always the case resulting in illogical design choices: favor lots of small thrusters versus using a few big ones to achieve the same output. Some also feature more "exotic" properties: fast regenrate, uncommon shape, increased resistance, boosters...

D - Other special blocks like generator, tractor beam, factory, solar panel, R containers and shield generators were balanced so that, the higher the P cost, the more advantages a block has. Sometimes, they are lighter or produce more power when compared to lower P ones. Solar panels were adjusted for this faction: They are heavy and produce limited R compared to other factions. I figured out that giving access to the seed planter as well as powerful solar panel would be overpowered.

In a nutshell, I did my best to make each and every block category have some sort of logical progression. For hull/armor blocks, each categories have advantages and caveats. Some features lots of different shapes and scales while other have a limited palette...

The three different cores are unique to this factions, both in shape and parameters: they are weaker than other factions cores and regenerate energy slower but two of them feature the teleport ability.

Weapons are in a different category: the vast majorities were left untouched. In some cases, slight P adjustment were made. Name were altered on a few ones too to better differentiate them. I took liberties in modifying some unplayable factions weapons though: Faction 6 (Borg), faction 14 (Mono Crystalline) and faction 16 (Jellyfish).

Borg had two types of laser turrets that were redundant. I increased range and reduced width/damage of the non autofire version and left the other set untouched.

Mono Crystalline had a very strong burst laser. I changed the name and description to reflect their strange origin and tweaked the P cost.

Finally, JellyFish were totally underpowered. I redesigned most of their block: Lightweight and fast regen "Composite Panel", Unique high TWR low P cost thrusters and boosters (you start with one set unlocked, actually) The only weapon they had, a basic turret, was modified to become an "Hyper Velocity, super long range, low damage" affordable weapon.

I wanted to avoid creating an OP faction at all cost, like some other mods do. Starting is harsh and you need to use your brain to survive but, in the long run, you have pretty much unlimited potential as the good blocks from most factions were preserved.

So far, most people complaining about Reassembler complain about what they consider "too hard to get started". The fact that you start with a limited unlocked block palette coupled with no pre-designed ships like in other factions probably largely contribute to this perception. Perception because, with minimal skills and a properly planned upgrade strategy, this is not harder than playing with any other vanilla factions.

I wanted, like I said, a balanced faction as much as possible. But, if you are the kind of player that want an harder challenge, you might try some of my other mods namely, "Super Slow Start" and "Delta-V".