Wintermute_BBS@deadbeef these days, systems like #MBSEBBS, #Synchronet, #Mystic, #EnigmaBBS etc support both: telnet and ssh so that can be considered a de-facto standard.
Keep in mind that people might be connecting with old hardware, and I mean 1970s/1980s type of "old". These systems often use modern #Wifi modems to connect via TCP/IP but use their classic terminal programs from back in the day which work through telnet translation (done by the WiFi modem). So if you don't want to lock those people out, it might be wise to also offer telnet.
Also take into account that some of these sytems have even less than 40 colums per line (e.g. the VIC-20 or the ZX Spectrum). So the system should be dynamic in terms of input and output of text width (this is something I want to implement in DX-BBS).
A simple chat system (when multi-user) and a simple filebase should also be part of that sytem.
Last but no least: could you imagine adopting an abandoned BBS codebase which already has all the core features but still has a lot of potential or do you prefer to completely "roll your own" ?!
