But if it is said on the warning page you can type in any rubbish to ignore the warning, users will do (to see their dancing pigs). As @tialaramex said such a thing is an obstacle.
It might be okay, if there are no instructions given on the warning page how to do that and the word is more compley than "yes", e.g. "IgnoreSeriousError" case-sensitive. This would be similar to how cheats work in games. Don't6 know though if Browsers should add such cheats as the user feedback is bad (the user does not see what happens) and it is really a strange UX thing to let users type in texts.
Therefore modifying keys or TXT files is a much better choice. Only experienced users can do this and all other users have no way. If such users really care they would search the web for a solution and then they may find it. In such a case they quite likely have serious reasons for skipping that warning and are at least experienced enough to find a solution.