Ok update time!
This...isn't helping. :P
The votes are very divided, and I can see why. Therefor, in any case, I won't make unlocks so easily obtainable. I don't want to anger one half just to please the other. :P I'm looking for other ways to appeal to everyone.
Don't worry about game modes, they're on my fantastic three list of things that really should be available in the game at some point.
For those who a interested in the dilemma, here is what is playing:
Reus is a bit brutal and roguelike when it comes to progression. It's not unfair, but it's not forgiving either. Also, complexity rises as you become better in the game. This makes the game ideal and super fun for explorer-achievers. It's hard to get to a point, but you're always rewarded with a new option to explore. Aside of Natural Sources are everything we can reward (it's not), this gives a feeling of entitlement, achievement and excitement. I don't know if you ever talked about Reus with a friend, but you're probably bragging about how you got Ginkgo or Panda, while he might be telling how awesome Coal is. It's a great way to soothe the learning curve, add challenge with high exploration value, and give a true feeling of achievement. (kind of like advanced wars did with unlocking different commanders.) It's certainly how I play the game, and I know a lot of other do it as well.
basically: value = effort * reward
and: effort = time * skill
On the side of that, timed games get the best out of Reus' mechanics when it comes to challenge and exploration. The game is more interesting at the end of a 60 minutes game, when you still haven't got everything, some projects are still running, and you think:"damn, I'm pretty sure I could do even better". I find that freeplay and 120 minutes game are more capped by space, end build and possibilities, while 60 minutes game are bottle-necked by you making the right decision with the right execution. Still, they both have their charm. Freeplay is probably now used to make a perfect planet, 120 minutes is used for the challenge with the biggest numbers and highest levels.
However, there are a lot of players who either don't like timed challenges, or challenges at all. They want a challenge purely based on what they build, or just want to build in a god mode. For those people, having the unlocks within reach is important. And within reach, it means probably lower time or lower skill. Which results in lower effort, which results in lower value. This is in direct contradiction to something a lot of people love in Reus.
So now I'm looking for other options. I could indeed create a whole new challenge mode, based on prosperity instead of based on time. However, I know the game is less fun without the time pressure (It's the last added feature so we did a long time without it, and time pressure syngergizes with the greed mechanic so well), and I would imagine seeing myself playing 1 or 2 long untimed games to unlock everything, and then say: "ok unlocked everything" and be done within 5 to 12 hours, against the 30-40 hours a normal player would take to unlock everything now with more difficult dilemmas and excitement. If I would have bought Reus, I would get a lot less value for the game with the extra mode then I would have now. That makes this still a hard decision (also, 67 new achievements. Not looking forward spending time on doing that).
I genuinely think era mode is the best suited for Reus when it comes to challenge and exploration, and people frustrated with it are the people who cannot or do not want to put the effort in it. That might be lack of time, lack of skill, or maybe time is not well spent enough (for example, the early game gets to tedious), or a too high learning curve. That's perfectly fine, and has nothing to do with these people being noobs or lazy, it just means the game currently doesn't suit their needs. Could be just the best and most industrious League of Legends player in the world looking for a relaxing quick building game in between the tense games of League of Legends.
I'm thinking about letting this issue rest for a bit, and to look at different options. Some things I'm considering: cheats, better early game, more game modes with different challenges for a change of pace. I think these solutions have a higher chance to please more people without disappointing the ones who are already big fans of the game.
Thanks all for the good suggestions and elaborated feedback!