There seems to exist a special version of Fighting Vipers 2 exclusively for the arcades, made for a 1-day event club, never sold and on top of that, apparently only a SINGLE board exists because of that. From what I can gather from probably the single most complete source that can be found for this version at the moment, this version of the game was made for a FV2 tournament, and among the special features it had, it had B.M. (final boss), Delsol and Kuhn as playable characters (which isn't possible in the original arcade version), Honey had extra nurse costumes (not sure if these were in the original arcade version...but they were included in the DC ports), Picky skateboard bottom part has a different design (shown in the intro, can't recognize who's in that board), and the craziest of all: It seems that you were able to pick any character with ANY moveset (in other words, play as moveset swapped chars), shown by some of the text from the source and screenshots of Honey using Bahn's intro pose and Charlie having Emi's winpose. 

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The source for information and some screenshots is this link, that describes the tournament events, participants and results:

http://www.spolan.com/ssl-3/event/2000-08-13/index2.htm

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And also got some screenshots from these pages:

http://collectedit.com/collectors/shou-time-213/arcade-pcbs-281/fighting-vipers-2-1998-06-05-special-version-japan-by-sega-9510?image=3

https://www.supermodel3.com/Forum/viewtopic.php?f=3&t=1228

I can't tell if Shoutime is currently in possesion of the board, as the 2nd link I posted above is about the discussion of the game having the chance of buying the game and dumping it; but the 1st link has screenshots of the board and seemingly credits the board being in Shoutime's collection. Either way, I guess I just should hope to see the game dumped soon.