Hello I am mexican and I love EU4, I kinda got quite excited when I discovered this mod and well for ideas, I can give you 3 sets of generic ideas for the different areas of the country, I could think on some more personalized ideas but well let's start with something basic.

Mexico is divided in 3 areas North, Center and South.

The north is right now is the most industrialized area of the country and the one that has subsisted longer with the mining industry, it is the area where the cowboy culture dwells too in this country (Like Pancho Villa and his dorados) So I am thinking that ideas around -production, tax, cavalry combat- are the best fitting for them.

The center is the area where most of the trade occurs and the area that administrates the country in general as well as being the most populated area of the country. For them I am thinking that -trade, unrest, manpower, tax- are the most well fitting ideas.

I don’t know the south personally but I do know that they are the states where you can find the country’s culture, they have the ancient places and have the largest indigenous population and from different tribes as well as being extra catholic. -Culture acceptance, religious, naval and unrest- ideas seem nice for them.

This is not favoritism as I live in Sonora and was raised mostly here (A good chunk of my childhood in Sinaloa) and am not a soldier but I think that certain state deserves a special mention:
Veracruz is a very special state for mexico as it is the headquarters of its defense forces and has been for all of the history since the colonies. They have El Heroico Colegio Militar and the Navy too so war-like ideas sound fitting for them -manpower, combat bonuses, generals extra points, navy- ideas sound fitting for them.

Thank you! If you have any other suggestions in regards to Mexico I'd be happy to hear, most of us don't know too much about your country, and we'd love to give it as much love as possible.