Will a new logic board fix my coffee damaged MacBook Air?

I have my brother's coffee-damaged MacBook Air here. The coffee entered through the ventilation at the hinge. I don't think any coffee was spilled over the keyboard. The story about it is quite long so I'll skip over many things that have been tried and failed, and try to keep the important parts. I know that many things I describe here is the wrong way to do things (due to ignorance or lack of thought), but I don't want any education on that. I just want to know what you think of the final state of the Air, and if you think that a logic board switch would fix it.

It was possible to start the computer and backup the data after the damage, although the computer behaved strangely (I don't have all the details on this).

When I opened the computer it wouldn't boot and the logic board and the io board had heavy corrosion from the coffee (it was only opened a few months after the fact). (The price to fix the computer at the computer shop (no Apple shop nearby) was deemed too high and I tried to fix it myself.) I took the computer apart and cleaned the io and logic boards with deionized water, some electronic cleaning stuff (made for this purpose) and Q-tips. I then used a blow dryer to make sure no liquid remained on the boards. (In hindsight, I should probably have left the boards drying over the night, but I was confident at the time and for practical reasons I didn't want the computer's part lying spread all over the place.)

The Air booted after the cleaning. The screen looks fine and the ssd seems to work well. The keyboard, however, wouldn't work (it did work before my cleaning). (This was a while ago and I actually don't remember if the trackpad was working. :( ) However, the kernel_task ran at 100 % (making the fans run at their maximum), something that might be related to the keyboard problem (?). After a few minutes, the computer turned off spontaneously. This continued as I tried to run the OS to try to diagnose the problem. I tried to run the Apple Hardware Test, but the computer shut down in the middle of it. Eventually, the computer failed to boot at all, even having trouble with lighting the magsafe LED. Connecting the Air to power now only results in some twitching of the fan.

I got some irc support from the Ars channel, from someone who seemed to know his/her stuff. The IO board or the IO cable were thought to be the most probable reasons. I ordered an IO board from ifixit and switched it, but it didn't make any difference.

Now, I think I have two options: try to sell it in parts (or together), as spare parts, or see if a logic board switch would help. Obviously, as a logic board is quite expensive, I would like your input on this.

Do you think it is likely that switching the logic board would fix this damaged Air? There is also the problem with the keyboard, that suggests that some connection to it might be damaged. Is it possible to buy replace the cables connecting the keyboard and trackpad to the logic board?

Thank you for any help!

Best regards,

Jonathan