I tried something similar a while ago

do act1 quests but skip Kagha conspiracy, don't murder Minthara, and don't free Halsin.
Trigger the druid ritual by going to mountain pass zone.
All the tiefling squatters are now dead on the road (yay!).
If you free Halsin he will meet you at the grove front gate and tell you that the grove is now permanently lost to the world because there's a few twigs in the way and say that he may as well hang out at your camp instead.
The problem is if you agree tp help Minthara's raid she joins you at the grove entrance and confirms that the 10 foot high wall and the twigs in the way do, in fact, make it impossible to attack the grove with an army of goblin sappers. Then she says it's all your fault and attacks you like she's your crazy ex gf or something. Pretty sure this is a screw up on Larian's part since I didn't even meet her until after the grove was closed. I didn't play long enough to see if she shows up in Moonrise, though.