Oh, you could
make the ground go back to normal after the boss dies apply the beisa method™ to ensure a safe path to your loot exists!
When the boss dies, spawn an Object (MetamorphoseAtDeath) that checks whether or not it is on the damaging tile (OnTile Transition). If it is, spawn a 3x3 square of tiles, centered on the object (PlaceMap) then move toward the center anchor object that surely exists (Protect) with a speed no more than 3 tiles, and no less than 2.82 (sqrt 8). After one game tick of this, transition back to the initial state that checks whether or not the process must be repeated.
Why this will work: You want the object to move a distance such that any arbitrary chain of 3x3 islands still connects (don’t move too much), but it needs to move enough in between steps of the procedure to not be standing on its freshly generated 3x3 island when the tile check is done to terminate before the main island is reached.
Hence the lower bound on speed is based on the worst case distance needed to get off the 3x3 island: When the object spawned on an exact tile corner, and takes a perfectly diagonal path away from this corner towards the center. Then at least 2.00 tiles must be moved horizontally and vertically to not be on the island anymore; so sqrt(8) distance.
The upper bound on speed is based on the best case distance needed to get off the 3x3 island: In this case, when travelling at least this distance + 2.0, the next 3x3 island will not connect. This case is when the object spawns exactly on a tile border, and crosses it on its path to the center (perpendicular to the border). It would require 1 + ε tiles to leave the island, So then after 3 + ε tiles you’ve gone too far.
Fortunately there is some space between the upper and lower bound, so a speed of 2.9 will do the job perfectly!
(This is not an elaborate shitpost, this is seriously what Beisa does. Try to decoy it onto the void in phase 3 when it chases you with black projectiles and sword throws, then kill it.)