Well that sounds fine and dandy but, "ultimately" the person who decides which method to use will be the EOR... And it may have been already decided that CAC-A (Air Carbon Arc Cutting) was already specified as the process to use in the contract specification documents beforehand...
However, if CAC-A is not specified anywhere in the documentation by any method, (And you better make darn sure that it isn't specified, or the EOR may lose confidence in you with respect to your proficiency in the proper interpretation of engineering drawings - Yikes!!!) then you want to be absolutely sure that the EOR wants to use this process as a "requirement" as opposed to a "preferred" process by bringing it up to the EOR for clarification because this way, you have "CYA" (Covered Your Arse!) as well as all the bases - so to speak which will end the confusion all together and leaving the decision & responsibility - "ultimately" resting in the hands of the EOR. ;)
In other words, the welding inspector's responsibility is to inspect the weld(s) as well as assuring that the proper procedures are being followed by the welder(s)... And the Engineer's responsibility is to apply sound engineering judgment in designing into as well as approving the proper welding procedures through the use of calculating, and incorporating conservative as well as economically reasonable factors of safety into the design of the weldment(s) in question based on well established, empirical research and proven design methods of application.
Therefore requiring complete co-operation between the welding inspector(s), and the Engineer Of Record in case any confusion may arise in the interpretation of the specifications by seeking clarification with each other as sometimes it is the case where an engineer may seek guidance from an inspector as well as visa-versa. ;)
Also, if there is a lack of specificity present towards achieving & applying the most optimal quality standard(s) into the fabrication, assembly,welding and any other manufacturing methods used in the construction of the product whether it be a single joint configuration, structure or components of different sized/ shaped structures, and then assembled together in a specific sequence in order to result in the efficient construction of a relatively complicated system or interacting systems that work together in achieving their intended design application... Then it is essential that total cooperation is established between the responsible parties as well as completely comprehending each others intended roles in order to implement the necessary changes properly in a timely manner to achieve without delays or re-work the design's intended goals as well as meeting the required safety considerations!!!
Bear in mind however, that the EOR is not required to follow the guidelines & requirements set forth in whatever code to the letter per se - that is being applied in the the design of whatever it is they're designing!!! In other words, the EOR may exceed the minimum requirements & guidelines found written into any code or standard that is applicable towards their design... However, if they fail to meet at the very least - the minimum requirements & guidelines of whatever code they are applying into their design, and catastrophic failure is a result of their own proven negligence to incorporate more than enough factors of safety in to the design, then they will become legally liable for any damages as well as injuries resulting in possible civil actions as well as criminal charges imposed on them by the courts!!! This is why it is so important for all parties involved to become totally aware of their own roles & responsibilities from the beginning to the end of any project that will be subject to such scrutiny even before one sequence of operation is started!!! So, always know ahead of time what you're getting yourself into before you find yourself in a position that you'll regret later on, and never assume responsibility for something or someone that isn't yours in the first place!!! ;)