I don't think this is OK at all. This seems like a classic "tagging for the renderer" case. There are many different maps, apps and processes using the OSM data and these kind of edits can affect these in different unwanted ways. 

We have the agreed rules in the wiki for a reason. To create a homogeneous data set. If you would like to "bend or change these rules" it would be correct to start a discussion about it eg. on the national forum rather than performing these edits without asking anybody for opinions.

Besides who desides when the bilingual status is "close enogh" for this kind of tagging?  And if this would be OK then why stop at just street names? You should use double names with suburbs, natural features, POI's and practically anything.
