Hi,
As Phani and Raman suggested you can go on with updating all required languages in RSCPINST..
But we resolved our issues by building new custom "ATTRIBUTE TYPE" data source on company code text table on ECC system, so you NO need to maintain new languages if you have it on ECC side.
This attribute type data source then can be mapped with info object text on BW side with info source help...
Both are options is feasible..its up to you to select approach based on your system settings....