Re the Prince/Princess thing, I would class myself as a royalist, but in this day and age, it does irk me that someone is entitled to such a prestigious title based on the simple fact that they were born. Most non-nobility titles have to be earned and worked for: Doctor, Captain, Reverend, Dame, President, etc. Maybe a better idea would be to give all children of future monarchs no titles at birth, then once they reach adulthood, they are subjected to a public panel (a bit like a parole board hearing), where they are asked to explain what they have done to deserve the lofty title of Prince or Princess.
This would be especially useful when there are two or more children vying for the same title, but only one can win. Think of their frenzied clamour to open as many shopping centres and unveil as many plaques as they possibly can, in the hope of becoming the chosen one who gets to wear the crown. It would also get rid of the 'spare' issue, as they would all have an equal chance and would only have themselves to blame if they didn't work hard enough to get picked over their siblings. It would make for a good reality TV show. "Crown candidate Annabel has travelled to Solihull today to open a new pig farm, meanwhile, her brother, Crown candidate Ernest has gone to Preston to oversee the planting of a new tree at a primary school...but how will the panel rate their efforts?"