ASM disable violations just for specific requests

It will be a difficult choice. Assuming that you do not want to implement any iRules, the second-best option I see is using two ASM security policies where one policy is the "lite version" of your main policy (duplicate of your main policy, minus several signature IDs). You can implement the trigger-logic in an LTM policy where instead of disabling the ASM checks, you conditionally select the lite policy for some specific HTTP paths, whereas your main policy is the default selection.

This will enable you to avoid false positive alerts/blocks, but still grant you a decent level of security.