I investigated more on this problem :
I've found that that continuous replication isn't possible with "doc_ids" parameter. I confirmed this reading the code :
DocIds = couch_util:get_value(<<"doc_ids">>, PostProps, nil),
... snip ...
case DocIds of
List when is_list(List) ->
% Fast replication using only a list of doc IDs to replicate.
% Replication sessions, checkpoints and logs are not created
% since the update sequence number of the source DB is not used
% for determining which documents are copied into the target DB.
% Replication using the _changes API (DB sequence update numbers).
Why can't we have continuous replication with "doc_ids" ?