Some of my ideas That might be good 😉

Sup bros, I'm gonna take you through some big details and some littles ones, in no particular order:

#1. Obsticle: patch of moss, grows over time to a max of 3x3 tiles.

#2. Level 7 wall breakers, unlocked at th10, level 6 moved down to th9, reasoning, it takes 3 wall breakers to take out 1 level 9 wall.

#3. Level 4 skeleton trap as maybe a part time halloween experiance only get it once, once leveled to level 4 it stays like that.

#4. Goblin hut, or barbarian, summons 2-6 barbs or goblins when in the attackers troops come in the 5-8 tile range, troops inside level up with your everday barbarians and goblins, unlocked at th4.

#5. Friendly challenges in global cht, this one, idk its up to you.

I like ur #1&#2 idea as the obstacles are the same there should be new ones. The wallbreakers also need to be upgraded.
#3 its not good becoz people who will have lvl 4 skeleton traps will get undue advantage.
#4 this is a good idea but u should give it more description.
#5 I don't like this idea at all.