I created an excellent city with a stable patrician block, there's even a luxury palace but it's not very sustainable as the city is short of 50 workers (this flucutates - during the year I usually get some extra labor but in January, for some reason, I lose about a 100 or so workers). I need to increase population somewhat if I do that, the already crowded entertainment will crowd the luxury palace out. Most of the buildings including patricians are sustainable and will not devolve ever. I waited for 5 years for 5 buildings to devolve/evolve on monthly basis. There is a major challenge in this city which is to conect it as now it's isolated building blocks. I tried this and oh the horrors I witnessed. A lesser challenge is to get the small casa block off the ground. Also you will see the negatives of my layout is that there are a lot of villas which would evolve but dont have space to do so, someone might try moving the outer road and buildings out to get a lot of large palaces but i didn't risk it myself. Hope you like it.
This city expands on the walker friendly layout somewhat by placing two rings of roads in circles around each other. You are able to guarantee walkers from each service will hit each house as evidenced by the row of 8 consequtive medium villas in the screenshot below. Check this out - the idea has some merit.