You can only appeal once a decision to grant or a decision to refuse has been issued.
If you want to take issue with the request, talk to the planner in question. S/he might be amenable to reasoned argument, or might dig the heels in. By asking, you'll know.
If you want you can still submit the higher ridge height, but AI requests usually mean a refusal would be the decision on a current proposal. If you get the refusal, then you can appeal and hope that ABP looks more favourably on your application, but I'm not sure the chances of success would be too high. Your choice.
There's every chance that the local development plan has changed in the time since your first application, with a policy of minimising ridge heights. Or are there other design changes you haven't mentioned, such as the orientation of the ridge line? Or maybe this application is being dealt with by someone other than the planner who granted your first application; someone with a different interpretation of the DP?
If all else fails, you could still build the original if the permission is still 'live' (granted fewer than five years ago)- it's what happened at the Ulster Bank HQ in Dublin where controversy over a new design led the owner to build according to a previously granted permission which was inferior imho.