I defiantly agree that adding in building, art patronage and other aspects would improve the gameplay of a Victoria sequel, as I also see it as being a great way to play tall for small counties, like Belgium and the Netherlands, alongside more peaceful games as you suggested. I also seem to have mis-understood some of what you were suggesting, as my interpretation of using granduer for projects like art patronage was that it would be consumed like a currency. Sorry about that.
Your suggestion of attracting a certain group of immigrants seems like a good idea, would some new pop types or even just representation of prominent individuals in game contribute to this idea (i.e. these groups or individuals would want to emigrate to your nation, giving bonuses to prestige from artists, research from scientists, etc)?
To the second part I don't think that it would be necessary to have new POPs, the POP system does risk of getting bloated if expanded to much, but I think that representation of prominent individuals would be a nice reflection to how the world develops in different games.