Engineering your own voynich

[nablator]

So, is this generally just a bad quality cipher that would be a pain to read? Are there many cases when ambiguities both resolve to common plaintext combinations?

The ambiguities are all in the first 2 of the 3 positions:
Ti+a is also T+ia so plaintext "te" = "ip"
Ti+i is also T+ii so plaintext "td" = "ig" = "it"
Ka+a is also K+aa so plaintext "se" = "gu" = "gv"
Ka+e is also K+ae so plaintext "si" = "go"
Ka+i is also K+ai so plaintext "sd" = "gn"
fa+a is also f+aa so plaintext "oe" = "du" = "dv"
fa+e is also f+ae so plaintext "oi" = "do"
fa+i is also f+ai so plaintext "od" = "dn"
Ki+ii is also K+iii so plaintext "rg" = "rt" = "gh" = "gx"
Ki+a is also K+ia so plaintext "re" = "gp"
Ki+i is also K+ii so plaintext "rd" = "gg" ="gt"
... and there are many more, not sure why my program missed them:
T+iii is also Ti+ii so plaintext "ih" = "ix" = "tg" = "tt"
Fi+i is also F+ii so plaintext "pd" = "eg" = "et"
f+ia is also fi+a so plaintext "dp" = "ne"
etc.

Some of these combinations occur in Byatan's ciphertext, so the deciphering process is ambiguous and needs a dictionary to resolve multiple possibilities.