I recently switched the persistence of timers and messages to an Informix datasource instead of hypersonic.
The creation of table timers did not succeed, because the order of the constraint name for the PK and the PK's columns has to be just the other way round for informix. For CMP EJB's the is a pk-contraint-template in standardjbosscmp-jdbc.xml. I extended GeneralPurposeDatabasePersistencePlugin.java to use this.
The modified file and the cvs diff will be attached shortly.

A second issue was the datatype mapping for java.lang.Object.
sql-type blob with informix means, you'll have to create an additional dbspace for blob data if you don't have one. The column's data will be stored there.
As an alternative you can use datatype byte. The data will be stored inline with the table data in the same dbspace. This is, in my opinion, the better way. So I modified the informix type mapping for this type to jdbc-type LONGVARBINARY and sql-type BYTE.
The cvs diff is also attached.