-- did you try to moving lob columns directly, with a reduced pctversion to the SAME TABLESPACE
-- Move the lob segment to the same tablespace.
-- sample table, with default options.

  1  create table FOO (
  2    col1 NUMBER,
  3*   col2 BLOB)
mag@mutation_mutation > /

Table created.

--
-- lets check the ddl 
-- the tablespace for data and for lobs is USERS

mag@mutation_mutation > @ddl.ddl

  CREATE TABLE "MAG"."FOO"
   (    "COL1" NUMBER,
        "COL2" BLOB
   ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
  TABLESPACE "USERS"
 LOB ("COL2") STORE AS (
  TABLESPACE "USERS" ENABLE STORAGE IN ROW CHUNK 16384 PCTVERSION 10
  NOCACHE
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT))
 ;

mag@mutation_mutation > insert into foo values(1,rawtohex('somejunk'));

1 row created.

mag@mutation_mutation > commit;

-- in this example i am moving lobdata to TOOLS tablespace.
-- You can move it to the EXISTING tablespace as before 
-- i.e, move to the same tablespace!
-- also do specify your storage changes ( reduced pctversion and disble storage in row)

 1* alter table foo move lob (col2) store as foolob ( tablespace tools disable storage in row pctversion 0)
mag@mutation_mutation > /

Table altered.

--
-- lets check it!.
--

mag@mutation_mutation > @ddl.ddl

  CREATE TABLE "MAG"."FOO"
   (    "COL1" NUMBER,
        "COL2" BLOB
   ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
  TABLESPACE "USERS"
 LOB ("COL2") STORE AS "FOOLOB"(
  TABLESPACE "TOOLS" DISABLE STORAGE IN ROW CHUNK 16384 PCTVERSION 0
  NOCACHE
  STORAGE(INITIAL 1048576 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT))
 ;

--
-- little thingy to get the ddl.
--
mag@mutation_mutation > get ddl.ddl
  1  set long 500000
  2  set linesize 1000
  3  SET HEAD off
  4* SELECT upper(DBMS_METADATA.GET_DDL('TABLE',D.TABLE_NAME))||';' FROM user_tables D where table_name='FOO';
mag@mutation_mutation >