But still why was there no backup system?
Does your computer have backups?
If it fails in the field, can you manufacture replacement microchips?
When your computer faces its nemesis, the electromagnetic pulse, do you curse the engineers for creating such a completely useless technology that should never have been installed in place of the good old abacus?
It's quite difficult to see the gel packs as in any way inferior to any other piece of technology in the real world or in Star Trek. They work fine until they fail, just like any technology. And no doubt they are extremely robustly backed up, only with more of the same, as it doesn't seem as if any other options would exist (save for the above mentioned abacus, or technologies comparable to it, such as semiconductor microchips or isolinear chips).
I suspect the original idea was for Voyager to have a sentient computer
Although it seems that every starship ever shown has had a sentient computer. They all can pass the Turing test, after all - we've heard their verbal interfaces in action. They joke, cheat and giggle with the best of 'em natural blondes. They second-guess, they grow impatient, they lapse, they outdo, they suggest, they mock.
How else would faster, smarter computing make ANY difference when the computers were already so capable in TNG?
In no way. After all, you can't tell the Commodore 64 apart from the Samsung NP900 except by aesthetics of the outer casing - unless you witness the two doing quantifiable number-crunching, which just plain never happens in Star Trek. Either we can't quantify what's going on at all, or then we can't observe it long enough to tell whether something is happening faster in the 24th century than in the 22nd.
So yes, having the gel-packs manifest as increased performance would be a hopeless task for the writers. Having them manifest as newly found AI capabilities would be quite possible. But if this were attempted, it should have been done in the pilot episode already, so I don't think it was something they still kept on considering when they started writing the actual episodes. It may have been an earlier concern, though, somewhere in the deep planning stages - but I'm happy nothing came out of it, as introducing AI this late in the game would be inconsistent. What's Data, nano-chopped cyberliver?
Timo Saloniemi