How to set all scalar types (number/boolean/string etc) to be set to type "string" during dynamic mapping (using river plugin)

Hi all...

This might be something really peculiar I'm trying to do. I'm running a "river" to dynamically index all data in my couchdb.
As multiple users enter data into the system, sometimes there is a conflict in mapping (MapperParser Error). For example:
userA adds the following data - {"tweet" : {"fooval" : "1"}}
-- elasticSearch creates a Mapping for this "tweet.fooval" variable as Number (as it interpretes it as a number)
userB adds the following data - {"tweet" : {"fooval" : "false"}}
-- elasticSearch tries to create a Mapping for this "tweet.fooval" variable as Boolean (as it interpretes it as a Boolean) and hence a MapperParser Error.

I guess you see the problem. Also I only want to do it at the level of scalar types, as I dont want Arrays/Objects to be treated as strings. I want all scalar types to be treated as Strings while the mapping is being created.

I couldn't find anything on the doc page, or on the forum, so thought will ask here for directions/pointers.

Thanks
Sunny