Thanks for your detailed comment! I agree with all points, there is potential for more fun and improvement in the game apparently and I am happy to see this in the comments, too.
The undead become 10% quicker with each closed graves so starting with level 4 or 5 they get as fast as 120% of the players speed. Then you might have to drop a stone in order to escape them.
Returning undead should be harmless, that's right ... that is an idea I had minutes before the deadline ...