@ams724
I'm afraid Inno is extremely unlikely to help you out on any of those things, for a lot of reasons. There will be reasons I'm not aware of, but below are some of the ones I do know.
In order to keep the game from being too easy, with constantly overflowing FP bars, and inventories stuffed with fantastic buildings that will rescue any situation, some prizes must be bad. In addition, it gives some of the excitement of a game of chance. Most prizes have some use, in some situations, though.
Observatory blueprints aren't given as prizes in the higher levels, either. They're supposed to be rare, and always have been. They're used as prizes in events, and they're used to encourage cooperation within guilds, as members have to help each other get the blueprints.
GE costs increase with the number of members. The rates can be found
here. Having more members won't help; having inactive members, or members who don't contribute, will actually hurt. It will also hurt your placement in the GE competition, as that is purely based on the percentage of encounters solved, divided by the number of members at the start of the expedition. Their era doesn't matter.
The prizes you mention:
Regular buildings are just marginally useful, but they can be used for quests; increases in happiness or population, production of certain goods, etc.. In addition, they can can help you get up buildings you don't have the technology for, yet, and they can be sold for gold and supplies.
Store Kits are very useful, to avoid deleting rare special buildings, especially event buildings. If you don't have a Renovation Kit, an outdated building can be stored, until it can be upgraded. If it produces something you currently have plenty of, it can be stored for later use. This shouldn't be too easy, though, because it's a strategy game, and city development is supposed to be difficult. If store kits were common enough to be used for "new looks", they would be much too common.
Motivation Kits can be useful in a pinch. That's not the main reason that they're there, though. Motivation can be bought with Diamonds; the kits are a sample, to increase Diamond sales. However, if they were too common, they'd instead hurt the Diamond sales. They also help demonstrate the usefulness of a large Friends List, to new players.
GE attempts can be useful, especially to players who negotiate the GE. To fighters, they're usually worthless. As I understand it, I'm a fairly fast fighter, using two to three minutes on level I, and seven to nine minutes on level IV. Eight attempts will last me sixteen to seventy two minutes, plus the time to handle troop replacement, plus the time to use prizes, plus various other distractions. That's enough battle in one sitting. For me, and many others, they're mainly just filler prizes.
Too common prizes are like regular buildings, in that they can be useful for quests. In addition, some of them are useful in small numbers, and the fact that they're common means that you can simply replace the old ones, when you advance an era. It saves Renovation Kits.
Generally:
The less valuable prizes, including the ones that are completely useless to you, are what makes the really good prizes, especially the really good Relics, possible. The 100 FP Relic would completely upset the balance of the game, if there weren't useless prices to counterbalance it. Without the fillers, the prizes would all have to be pretty boring.
The Relics have the same probabilities and value throughout the expedition, while the Rewards get better in the higher levels, especially at level IV.