Hi Harsh,
First of all I don't think PI would be able to process 200 MB files, we have seen issues at various stages like in the messaging system, pipeline steps etc when the file is around 100 MB itself without any mapping or lookups in between .
I would suggest you to split the source files and then think of any mapping.Also since you say this involves multiple lookups, it is not at all a good idea to even go with two 100MB files.As per the tuning guide from SAP, the ideal size of a message should be between 1MB and 5MB.
In versions starting from PI 7.31, there is a way to handle large files but it will be only a pass through, so even SAP though they say they support large files they also say routing, mapping etc will not be supported for such large files.
BR,
Harish