I think what you are looking for is mixed code.
A good start point would be Brower--Hamalainen--Ostergard--Sloane. They are talking about mixed binary/ternary code, so for some $k$, $n_1=\cdots=n_k=2$ while $n_{k+1}=\cdots=n_N=3$. Brouwer keep an online list of known 2/3 mixed code.
I think they also talked about some general cases. Anyway, more papers can be found from the references therein or by the key word.