Just to be clear, I am not new to this game. I had an advanced city and know very well how this game is functioning, except some latest changes. Spire was one of the features I liked (MA and library set were my favourite buildings, but library must be modified to function properly - only the part with goods) and my preference was to fight. In order to fight map 3, fully/almost fully evolved fire phoenix is a must. Now I am starting from zero with the intention not to get involved into extremes. In a way, I am comparing this game in terms of 'then' and 'now'. And I can tell you with the confidence, this game is not focusing on small players only, for them do stuff is as challenging as for advanced players.
My point is that in a current setting, chapter 4 is not designed to complete all maps. It's very well to say that early chapter players can do this and that, FS is a team, works like a team, wait for later chapters you will see how difficult it gets, etc... The reality is that completely new player is not in a position to know and to understand all strategies involved and how to overcome some challenges. It requires some time and experience/skill to understand how to play all maps and to do stuff in general. I remember as well, that I had few nightmare FS until I started to understand this game better. I am advocating for smaller players, as I read many comments suggesting that this game is focusing of newcomers, for smaller cities everything is so easy, they are benefiting most and so on. I looks like in reality some comments advanced players make are simply misleading.
As for my personal strategy nowadays, no fire phoenix, no way I attempt to do all maps in the spire on a weekly basis: does not matter in which chapter I am, I won't be forcing myself to do something I strongly dislike or don't have enough resources to do due to time constraints (say, no option to run shorther cycles in manufactories, to collect resources regularly) and with a small city it is not even possible due to multiple factors, low boosts, slow scalability of production, unwillingness to ask for 0 star trades as I am more than satisfied with my pace of growth and tournament scores, etc. The way I see possible changes to the spire from my small city and relaxed approach to this game: if moonstone library will be removed completely, i.e. without re-introducing modified set or any other similar set (equivalent, not inferior), the need for the fire phoenix disappears in my city. I can achieve a decent score in tournament without fire phoenix and without diverting/splashing resources on the spire, especially on disproportionately expensive map 3. With the players leaving this game at current rate, I do not see many FS doing maximum on both levels, spire and tournaments.
So I am returning to my original question: in which chapters players would likely to benefit from full set of evolves offered over period of few weeks? My understanding is at advanced chapters only (providing that player doesn't have fully evolved phoenix yet; not everybody is religiously playing this game and participating in all events
).