Actually this deals both with blasts and hacking, may not have an immediate,
easy solution, and can also be downgraded to idea/feature (and can also to
upgraded to important, but then, my game style is not hacking :P )

Basically, the only way to gain experience when a (hostile) bot dies, is that
YOUR bullet kill it.

If a bullet from the “self” faction (taken-over bots) kills a bot - no
experience gained.
If a blast provoked by your gun (eg. Electro Laser Rifle, Exterminator) kills a
bot - no experience is gained either.

A proposed solution would be to give Tux experience whenever something from the
SELF faction is behind a kill (bullet or blast - wait, does blast have factions?
If they do have, I am still favorable of friend-fire fire for them)

This may be considered at bug levels because the title: From the four possible
gameplays (melee, ranged, skillcaster and hacker) only the last will actually
result in an underpowered character, with no levels, and also be hardest because
lack of Training Points income will make harder to improve skill.

Another proposed solution is to give Tux experience for anything which dies
while he is looking at it (you can learn a lot of things by observation). Both
solutions may be hard or not sufficient (or hack-ish) for the problem.

Proposal #1:

When an enemy dies and it was not you who killed it, say at console: “You
downloaded 5 exp. points from combat data at vinctinicy.”
The text is all wrong, but the idea is giving 10% of base experience when a
friend scores a kill.
The conceptual idea is that when the bot is destroyed, it dumps battle logs to
the Dark Robot Circle. Tux then downloads these files and learns from them. When
it was a human-human death, a nearby bot (?) could have generated the logs and
sent them for the DRC continuous improvement.
It is not said if Tux receives this data from the hacked bot, or from the
destroyed bot, the idea is merely to justify a gameplay issue fix.
You know, when you use a M1cr0s0f7 program, they demand you to agree to send
them reports of program usage for “enhacement”.
All bots, of course, send reports of their usage to MegaSys Reasearch
Facilities, who would use this data to prepare development (eg. if a bot is
killing more with the right hand than the left one, next version would come with
a right hand stronger than left one). Dark Robot Circle took control over this,
though.

Proposal #2:
Reverse Engineering program could allow tux to gain experience points when used
against a bot.
That could also help with the Hacker Playstyle problem: We paralyze you and give
you experience for the bot. Increasing skill level INCREASES paralizy time and
experience gain. For hackers that wouldn't be a problem because they have bots
to protect them, but for non-hackers this means sure death. (It would also
cancel any shielding or invisibility currently active in order to run.)

Proposal #3:
Hacked bots remember what they kill and Tux can replay their "memories" by
talking to them and running a program that Tux wrote, gaining experience from
new kills (since the program was last run). Maybe you would also need to run the
program on the bot before it starts recording memories.

The program could be created when you get novice at programming (from Sorenson)
and hack a certain number of bots?

It could evolve with combinations of the rank in programming, number of bots
hacked, experience gained through the program, and level of "Reverse
Engineering" (mentioned in proposal #2).
The amount of experience you gain could be determining by what gets recorded in
the current version (image, sound, gyroscope/movement sensors, commands from the
A.I., or any other input that a bot might provide).
Inspired by proposal #1, when the program is advanced enough it could send
experience directly to Tux in real time through botnet (and by consequence only
when the bot is not too damaged).

As the downside, you lose unseen experience when the bot dies and lose the time
needed to run the program.
Inspired by proposal #2, you could get paralyzed or slowed for some time when
you gain experience from the replays (because you are busy processing them).

There are multiple issues preventing me from using the hacking play-style:

1) Bots will not follow you through stairs/teleports/whatever. Not that huge of a problem if not for the next issue.

2) Hacked bots will be reprogrammed (and possibly kill friendly NPCs) if you leave their level for more than 10 minutes. This should be an easy change.

3) Going through the dialogs system to heal the bot takes too much time when you have more than a few bots assisting you. There could be a heal bot skill that uses circuits. Or perhaps applying the wrench on them should heal them.

4) I had to go through the dialogs to set each bot to follow me. There seems to be no way to set that as default. Perhaps another more skills could be added "broadcast follow me"  "broadcast hold position" "broadcast roam freely".

5) Invisibility is overpowered. You can just go bash bots freely with no retribution. I propose that bots be made to "see you" as soon as you attack them.

6) Skills are overpowered and bot damage under-powered. Especially late-game, when you have a 100-150 dps laser, 60 armor and all the bots have is 20 dps exterminator or twin laser.With exception of the forest harvester, their HPs are also very low.