Request: REMOVE PARTITIONING IF EXISTS

ADD/DROP PARTITION IF [NOT] EXISTS are supported, but ADD and DROP allow a limited set of operations. REORGANIZE and COALESCE allow some operations that are not allowed with ADD/DROP. But the only way to alter partitions in ANY possible way is removing partitioning and then re-create partitions. For this reason, IMO, the most flexible solution would be:

ALTER TABLE t REMOVE PARTITIONING IF EXISTS;