1. definitely. remove the risk of losing a plus-level is essential, even if the chance to farther upgrade the item would be ... maybe halved or even quatered
2. i agree, although it will be hard to balance the phirius token price.
3. this is already implemented. harder dungeon quests => more peak xp
4. i support that idea. and i'm pretty sure it's easy to implement.
5. the battle pass is interesting. maybe you should take a deeper look on how to implement that pass. e.g. would it be available per char? oder maybe per account? or even only once per gameforge account?
6. would be great, absolutely! but what you always have to consider: people are creating twink chars over and over, thats a massive problem for the ingame economy. if leveling a twink to 100 is too easy, then this problem will exponentially increase.
7. can't say much about that. the ruby system ended shortly after i started playing. still, my first char was able to get a flying manta, and i think that's a great mount.
8. i think that was mainly licensing problem between gameforge and runewaker. rumors say that problem was solved, and now gameforge is theoretically able to do much more development stuff than before. regarding a marketing campaing: Square Enix are recently doing great with their FF-XIV advertising campaing. gameforge could easily copy that.
9. there are still too many bugs in the siege wars, but on the long run there should indeed be some improvements like benefits depending on the siege war points that a guild has - and to make this more challenging, guilds should lose a percentage of those points for every ... maybe week that they don't sign up for siege war.
10. the title system is indeed a big construction site. but i think it's got a much lower priority than the other things that you mentioned.