Title says it all. If you take the feat and do something like roll pickpocket, you shouldnt have a 5% chance of total failure if a 1 was still enough to beat the DC. Skill Focus represents a sort of mastery and confidence in the skill that shouldnt suffer from the d20 auto failure.
I know the NWN engine might not allow for such a change in all scenarios, but in the example above atleast I believe it is a custom EFU script.
The special Rogue 10 feat, Skill Mastery, is also a good candidate for this effect. It is very much not great as it is and could stand to be a more competitive pick.
Not really into this, I'm afraid.
Skill mastery allows you to always take 20, so that should prevent 1 rolls anyway.
If there's no chance at failing Pickpocket it just becomes a game of PVE with almost zero chance of facing consequences.
Might be alright for some skills though