I don't think vichan (nor lynxchan for that matter) is a good idea cuz a jazillion other English-language imageboards use it, and I've heard from a million different admins over the years about how it seriously suck balls and is impossible to work with. Hell, I didn't even need to hear from them cuz a lot of the times you could just plainly see and feel how sucky and unstable the board software was while using it

If a time came where we absolutely had to ditch kokonotsuba, the obvious (and best) choice would be to go back to either "Heyuri 2.0" or Sakomoto - they have all the features we've come to expect from Heyuri, and the only real reason we left them was cuz they ran liek crap if you tried to have more than 10-20 pages worth of threads (which is still a problem with kokonotsuba)

If those options were somehow nonviable, and we wanted something vaguely familiar that has a lot of QoL features and - more importantly - is still actively maintained, then jschan is probably the best bet. If it came down to it, I'd be willing to spend the time and effort to get it looking as close to the classic imageboard look as possible, cuz by default it doesn't have a Futaba-like theme

If THAT was also a non-option, I'd be open to forgoing the gazouBBS/futaba format entirely going for something wildly different - something that nobody outside of Japan has ever seen or used before