I was thinking the conversation would happen before sex and would go more like " I do not want children right now or never and in the case of an unwanted pregnancy I would like for the option to opt out of any and all legal responsibility for the child. " Yes that may put a hamper on your relationship but it would be for the best because if one person wants children and the one person does not there will always be one person unhappy about that part in the relationship and the relationship would like last either way. The biggest up side to that would be that there would be a lot less "I forgot to take my pill" if a woman knows up front she will be going solo and there is no way the law can get the man for child support.
I am not thinking about a database or anything like that. There are tons of clinics around and I don't see why they would not be able to have forms on hand that will allow couples to make legally binding contract just like sperm donors do. It would be safe and there would be a neutral person there to co-sign that someone was not forced into signing the paperwork. Clinics could charge a fee for it which would bring in an almost no cost source of revenue and who does not like money.
I like it strict because that increases the chances of something like this passing. It may not seem like it but I am a very fair minded person that tries to look at both sides of the problem and the options available. If it is too lax people will start giving examples of deadbeat dads who have 25 children and don't care about birth control. They will make it seem like most men if given the option will take the " I was just here for the sex and it is a woman's job to worry about birth control because they have more options. So you can take this kid and either abort or whatever because it is not my problem anymore." But if you make it too strict it becomes almost like not having it because it will not be "available" to everyone.
You want it to seem like a win-win for everyone not just men and that would be the key to getting it passed.