I must say from the sound of how this is being implemented, I agree with
@Medribradrion. The concept of introducing new players to GBs is great. Explaining how it works and getting them started and understanding it through a tutorial has some real merit.
That said, I started playing not that long ago. I started getting blueprints and would see all these GB in various other players' cities and wanted one too. Finally I got a full set for one. It happened to be the Colosseum. I saw how medals could be used to grow the size of my city and thought, yes, a source of medals. This building will pay for its own space in no time at all and will be fantastic.
I went to build it and of course it is huge. At such a young age my city was so small that giving up so much space was a severe constraint, but I did it anyway. Then I started instantly putting FP into it to build it up. It didn't take too long to buy an expansion or two with medals, but most of those medals were actually won by other means. The GB helped, but quickly I was realizing that expansion costs were growing at a much faster pace than that Colosseum would ever produce. The GB just wasn't worth it. I trashed the GB and was rather annoyed by how much wasted effort and, more importantly, FP I had thrown into the thing.
Had I been a bit more lucky and my first set of BP just happened to been Zeus or something else, I would have been much better off. I still have my Zeus now. Granted, it may have just pushed the Colosseum discovery a bit down the road. Who's to say if I would have only figured out that I didn't want the Colosseum after I had built it, or learned enough about the game to forego it from the start.
Now Inno plans to force the Colosseum issue that I had onto every player. In your own words, "[the Oracle] not really that interesting for advanced users." So you are going to excite players about their first GB. They are going to flood it with their FP, slowing their tech advancement considerably. The at some point they will find the GB has no more value to them and they'll need to trash it or feel stuck with it because they don't want to abandon something they put so much FP into.
I say keep the Oracle. Keep the tutorial. But overhaul it to be more like the Longhouse. Do not allow players to put FP into the building, either their own or others. Create an oracle voucher or some such whereby this token is used to upgrade the GB and they are earned through the tutorial and quest system. Or have FP given to the player (like the diamonds for the longhouse) and then forcibly applied directly to the FP through a tutorial like lock-in that doesn't allow them to put that FP elsewhere.
Basically, give new players their first GB and give them everything that will be put into that GB. Allow them to put nothing of their own into it. Just like the Longhouse, introduce them to the new concept. Walk them through the steps. Let them keep the freebie as long as they want. But keep its value limited so eventually they'll get rid of it and replace it with things they earn and build.
The other option I see would be to have some sort of Oracle recuperation event. Rather than just destroying the Oracle as with other GB, allow players to transfer the FP to a another built GB of their choice or some other means of getting back a good portion of what was spent on the GB. Or maybe just a 1 time offer gets added to the quest tree. A single quest is added into the storyline at the end of Iron Age or EMA or wherever deemed likely that the Oracle's usefulness is likely to start to decline. This quest offers a one-time chance to destroy the oracle through this quest and get some quality something in return (be it a direct FP prize or something else that makes having built that forced GB into a worthwhile task rather than something that hindered them in the long run).
