Leave the maximum durability alone, and make the cost for low repair skill a cap on how much you can repair, so that you can repair that sword with Repair 1, but it'll only get up to 20% of its maximum, so it'll break sooner.
Thing is, there's already a small window in which a Repair skill of 1 can be used. These aren't exact numbers, but the way it works right now is that if an item has 69/70 durability it requires a level 1 Repair skill to fix. If it has 50/70 durability, it requires a level 2 Repair skill to fix. I'm assuming it continues to get more demanding from there as you neglect repairs longer and longer.
So, you can't really cruise along on a Repair skill of 1 forever. A single battle (if you take enough damage or use a weapon often enough) can create a scenario where a level 1 Repair skill is completely bypassed as an option.
