Per your request:
I don't bother with the replaces other items with this flag. I leave that for powerplants.
besides it is possible to have competeing religious factions. Having some precentage of your population find Jesus, wouldn't stop others from still following the old belief system. For this reason I have very brief periods of over lap, and then the older one is still there, but now just as a memento of days gone by. No one is going to build a new pagen movement with any force. So having the city lose the ability to build these old structures is better then having them build one type and then another and so on and on...
In the case of the sacrificial alter (Or monolith in my game) I have the abiltity to have both the temple and the monolith. But a temple requires incense, and a monolith requires nothing. The monolith and temple both go obsolete at the same time. But, I could have the alter/monolith behave the same way as the temple/church. A brief period of overlap and then the old one is just a decoration.
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You had asked me to go into more depth on this in this thread.
I think I was fairly complete above, but I'll try.
Religion has evolved over time. Early relgions were typically ancestor or other pagan thing.
So in my game I have it set as follows:
Early game, there is the monolith (or could be alter). This upgrades to nothing. And falls into disuse when more advanced belief systems crop up (I know some asians still engage in ancestor worship today, but bear with me).
If you have insense, you can build temples. The effect of temples is the same as currently in the game. The effect of the monolith/alter is the same except it gives 1/2 the culture. Since it serves primarily to sooth those that live there, not draw new inhabitents in.
I added a number of pseudo eras to my game by creating choke points. Spots where all tribes must pass through to advance to the next era. This is similar to how the current era system works. These include such things as The dark ages, age of discovery, age of reason, computer age, and a 1-2 others I may have forgotten. The purpose of these is to lump similar era technologies together, while still allowing moderately free selection of most techs within an era. The choke-point technologies take far longer to research, and typically require all or almost all of the subordinate techs to be known.
One of these technologies, the dark ages gives the ability to build churches. The dark ages also allows the research of monotheism.
Once the dark ages have are in your past, you must fairly quickly build churches... this represents both the dawn of christianity, and it's rapid spread. Pagan idols and temples both go obsolete with monothesism. Cathederals do not require pagan temples to build catherals, but instead require christian churches. Catherals now require a new technology to be built, architecture. Now some older buildings did show some architectural ability, but the rarity of these eddifaces is what made them wonders. Cathederals on the other hand require that this knowledge be codified and fairly wide spread, since otherwise there can not be these great churches in every major city.
These theories can be adapted to other (non-christian) beliefs as well. Muslim, etc.
I have made religious buildings to cover most of the more common faiths.
I don't differentiate between catholicism and protestism nor do I seperate Sunni from Wahabi, prefering instead more generic labels.