Upgradeability that far less than 10% FS can achieve and this is supposed to be a valid reason? i don't doubt they will introduce a tourney difficulty increase shortly to slow down the game as well that will further make the 10 chest option harder on most members of the game
FoE has had the ability to upgrade event buildings for roughly 2'ish years now... while the 1-up/reno kits were difficult (or just expensive due to diamond use) to obtain initially, they're to the point that they're now rather common.
So while the new RR spell will likely be initially difficult to obtain when it's first released here, don't be surprise that as time goes on, and we get more events, that we'll see them drip-fed through out the game beyond just "10 chest only" items.
As for the lackluster (okay, all but useless!) set buildings... well, I'll admit, we FoE players kinda borked that one, with Inno's help of course.
When initially introduced to the other game, the first 2 sets were both;
a) grossly powerful, as in, you could easily run
your entire city needs on just the set buildings!
b) very compact in size, making it quite easy to fit 15-20 into any decently advanced city. (the largest was 'promoted' as an 8x4, but could be worked to gain all bonuses technically as a 4x6 due to duplication)
Imagine for example, a Dwarf or Fairies chapter city that had nothing but maybe 6 token residences, 5 workshops, their barracks/armoury and then nothing but set buildings, which would still give them better production vs. just having that same amount of space in boosted factories?!
Kinda nuts, ain't it?!
Oh, and for the added kick in the pants, that city would also generate 60-80+ kps per day from the sets too!
And of course, like pretty much every game dev out there, instead of just tweaking our set buildings once they introduced them, Inno just nerf batted the ever living gak out of them, so now they're huge in size & generally fairly useless for production.