I didn't think it was a good idea to use a military flag, regardless of what era it came from. But most people would associate it with the 'wrong' era.
really? there're many creations and designs using british, US, French, Germany or whatever military flag or symbol, either current, past, ancient or historical, that might not be a coolest thing of all but are no way taboo (of course except hakenkreiz). Everything depends on context and sense.
As for the radiating sun flag, that specific design has indeed been adopted as identifying military, but it was by Meiji government back in 1870s, not just for imperialism era.
Also that radiating design itself is a design motif that had existed long time, (i mean no way came out of nowhere and invented at that time just for Meiji army flag), and been used among public mostly as a background to express cerebration or whatever that is positive, good fortune and joyous. Also think about halos found in buddhism statues and drawings that are older than Japan history, they are quite identical, so such design has been quite common.
Also regarding red sun and blank white background that is Japanese flag, again that design motif, a circle (red or gold or black etc) and blank background (red, white, etc) had existed in Japan and used by various emperors and shoguns etc throughout history, and can be traced back to as early as 7th century.
So, that radiating sun thing is more a combination of the two, so it's impossible to draw a clear line. Either that radiation pattern nor the "a circle & blank background" are not military thing at all, let alone association with specific era.
examples: radiation design used for fishing to express big catch of fishes.https://www.google.c...iBcSkkQW3u4GQCA
like this way, this radiation pattern is used to express whatever is positive, commonly and in various ways, as i said above.
Also used as self-defence force flag nowhttp://sokuup.net/imgs/soku_16245.jpg
the flag in this pic is it.
it has 8 beams. The "origial" 16 beams version is also used for some navy ships.
So it's very loose, it has such various and wide origins and usages, that, unlike that nazi symbol, cannot represent and be attributed to one specific thing of one specific era.
I personaly think it's completely ok to use that radiating pattern to express sth Japanese, but yea i know most people tend to associate it with imperialism Japan. I admit we lack efforts and explanation.