...whilst "aikidoka" is actually adding the word "ka" (professional) to Aikido, i.e. a professional aikido person.
I think you make an excellent
point here... one which, I think, is generally not understood by Aikidō people who don't speak Japanese. The suffix -ka suggests a degree of seriousness and accomplishment in one's pursuit.
家 (ka/ke) means "house" or "family." As such, it shows that you're considered by the family
to be one of them. I think that's significant.
When referring, for instance, to the Ueshiba family, you could say 植芝家 (Ueshiba-ke), whereas a serious Aikidō practitioner would be 合気道家 (Aikidō-ka). There may be a bit of poetic license involved in translating Aikidō-ka as being part of an "Aikidō family," but poetic license never kilt nobody. (A poetic license to kill
, on the other hand...)
It is, IMO, just as improper for an writing enthusiast
to refer to himself as an author
(作家 sak-ka) as it is for a relatively junior Aikidō student to refer to him or herself as an Aikidō-ka. Maybe this all just boils down to cultural-linguistic differences.
Or... maybe I'm just too serious about this language stuff. :-)