Thank you wow, I really appreciate the effort of this feedback and sorry for the late response.
I understand that merging is really tedious on this part, and current fix for that is that you can unlock the Quick Upgrade after Level 4 which is just a click of a button to upgrade the tower but at more cost of gold, I think my mistake is that I didn't unlock it on early levels and I'll move it on early level on my next demo update including the speed control should be unlocked after level 1.
And yes after hearing lots of feedback on imbalance, as I'm still learning to what is fun and not, and yes its too imbalance right now that you still have lots of gold on late game, I'll fix this on next update by lowering the amount of gold earned per enemies, and increasing the merging cost and nerfing the upgrade stats so players should lean towards to creating a path using towers instead of merging on early. And for merging maxed level towers could create some new towers but not every tower could be limited for what I'm initially thinking. Where you can merge Archer and Frost Tower so you'll have a Frost Archer or Blaze Archer etc.
And I'm currently testing and changing the gameplay for Items as currently it is currently gained by dropping random chest which is not really rewarding so I'm moving it into a Fixed RNG Item Shop which increases after you buy. and I will not totally remove the chest, I'm planning to move it into an enemy with much higher hp, holding the chest on its back and drops after you killed it and could make that chest free with some higher chance to get better items. So you can control whenever you want an item or just build or upgrade a tower.
Also I'm adding the new Rune Feature which is a specific random buff that can be gain globally by specific tower types, I'm still thinking its a Choose Reward so instead of items, it should Rune that can be stacked for example after completing round 1, you can choose which tower that you currently have would gain the rune of attack speed, rune of damage or rune of health etc and It can be stacked every end of round.
And for the Traps feature think of like some of the clash of clans Traps, that's what I think I could implement for this and using wood for economy of this. And you can gain woods by chopping some trees around which I think should be tedious also but I think I could make some towers that could automate that.
And lastly could be the tile buff/debuff for towers that are randomly generated on the map I think this could be fun for not just building anywhere on the map with your maze.
And thank you I really appreciate your feedback