It is possible for Delsin to naturally develop all of his abilities for a specific power? I mean, he had his powers for a few days, probably, and I think the Core Relays and Shards contain an energy that boosts their development. So I think that SP will spontaneously update the game one day by adding in the rest.
The way I understand it is like he's an energy sponge he is capable of using anyone conduits ability if he has contact with them for long enough. The longer he holds on the more power he gets but it is essentially as if he gets the very basic of the conduits power i.e. if he could have touched Cole he would have gotten most likely the basic lightning bolt attack from inFAMOUS.
As for the additional powers of each absorbed element they have only shown how Cole and Delsin gain new powers really and never how the others got the more advance abilities. If we figure it is most likely like how Cole gained new powers in inFAMOUS we can infer that all conduits gain new powers by absorbing the afiliated power source or absorbing a massive amount of the affiliated power source like when Cole reactivated the power in certain areas of Empire City.
This could also explain why Delsin didn't have access to the Neon shooting ability at first he didn't absorb enough neon energy out of Abigail when he got the power. When he absorbed the energy from the neon signs in the room where he battled her he could have gotten enough to get that power.
I think the reason we put so much thought into the power logic, stems from our wish to be a conduit.
If you search "Conduits" you can see that a conduit is able to expland their ability by absorbing a large amount of the form of matter they manipulate, just like Cole in the first inFamous
X5 here. This is what I think of the power type comparison with Cole and Delsin. Delsin can be thoguht of a scout. His parkour is speed based, like using his powers to climb building that would take Cole much longer. Delsin falls into my custom category of speed/scout based conduits. Cole could be thought of a powerhouse based conduit. He has a lot of power, but can't move quickly across the city. What Delsin lacks in quality of power, he makes up in speed and vice versa with Cole.
I think Concrete is... sort of a trophy that you can interact with, and the lack of Core Relays (look, he had to absorb core relays for each element/power he has) due to Eugene finding the what-I-think-is-the-last-four relays.
I really wish that you could subdue enemies with concrete by doing and arc restrain, but with concrete. I also wish that the L1 ability, instead of Concrete Thrusters, was encasing enemies legs in concrete (like the Bishop power) I also wish the Karmic Bomb encased all enemies in concrete to their necks (good karma) or encase them entirely (evil karma)
Concrete was put at the end of a game so you can "have another power". It seemed unfinished unlike Cole's, or Delsin's other powers.
Well, if you played Second Son, (I didn't but saw reviews and both evil and good playthroughs), his powers never seem as strong as the original conduits. He may be versatile, but doesn't have power.
I think the reason why concrete is just so lacking all of it's functions is that it was rushed into to game. I have a theory though. At some point, maybe the ending of the game would turn out like Infamous 2. The clock is turned back to when Delsins last mission starts, the one where you choose to "Kill Augustine" or "Expose Augustine", but you cannot do that mission again because of obvious reasons. You also don't have Concrete. But the developers and programmers decided to take out this ending because of what the fans would think of not having the power itself. They then made a new ending style, and included Concrete with the package, but they rushed it into the game out of popular demand and speculation.