From what I understand Cuniberti actually submitted the "all-big gun" design to the Italian Navy but they rejected it before he was asked for some of his stuff to be published in Jane's.
The Russians were busy in the "what-if" game, too, though, even earlier. There was a Lt. Kolchak at Port Arthur, for instance. His DD's mines had sunk
Takasago but his health had been broken by an Arctic expedition. So, during 1905, he was in the hospital, where he passed the time he spent in the hospital sketching up new BBs. One of his ideas was for a ship with 8x 12" (twins forward, aft, and each side amidships) and 12x 8" (2x twin turrets each side and 1 on each end atop the 12" turrets). He sent in his ideas once the war was over and they were taken into consideration, although ultimately rejected.
However, the arrangement of the 12" turrets is the same as originally envisioned for
Dreadnought. Had it not been for improvements in engineering during the sketch-up period, allowing volume for another barbette amidships,
Dreadnought would have just had 4 main turrets, arranged just as Kolchak's sketches.
Also in mid-1905, the official Russian warship designers submitted a design for a semi-dreadnought with 4x12" and 12x10", pretty much the same as
Satsuma. Again, never built, but it further cloudies up the issue of who thought of it first.