Maybe i'm mistaken but i don't think that any
deputy service offers that option just because
it's too much trouble for them, specially since
you have to consider that any kind of payment plan
should be arranged before the end of the auction
as no seller would accept it after the end of the
auction if it has not been discussed beforehand.
And even if the seller accepts it this just adds
more trouble for the deputy service as they have
to take care of sending the periodical payents and
such.....

This reminds me about a similar thing that popped
up some time ago about deptuty services offering
help to sell items on YJ. In my opinion it's just
too much trouble for them.

So resuming, as for now i don't think any deputy
would offer you that option unless they do it as
an special favor to you. A different thing would
be if crowds of people would be willing to ask for
payment plans or sell items on YJ, in that case
they might think of some kind of service for that
(with it's suplementary fee of course).