As long as they have a nice wedding with some of the bells & whistles of a royal wedding, I really don't think it will matter. I hardly think if they do not have a huge wedding in WA with the Glass coach, etc etc it s going to cause a diplomatic incident.
I don't think there will be the glass coach. I also don't think it'll be as big as William's. However, the comparisons will be there with WA and St. George's. Then the media is going to start the Queen/ royal family doesn't approve crap even though I highly doubt that. Some of those rhetoric has already started this week in the British publications.