Have you thought of mounting switch machine controls on track diagram in fascia at this place. Incorporating lights to indicate direction of switch path (or as interlocked routes in series using rotary wafer switch(es))this is easiest way to go to impart information to operator<that I assume has some kind of hand held DBC,RC,DCC,CC,or IR walkaround throttle>.
This is because model railroad LED signals require you to get up close and personal to read them unless the lightlevel is low. Semaphores mighy resolve this, but require either more skill to build, or more dough to purchase. You have some kind of price constraint ? Besides, there are only expensive operating semaphores that can be used on a signal bridge (also has to be 'HO' scale or larger, I ken).
By the way I do not see any double slip switch in that picture , but that could be because of low light level and my eyes. Also it would be helpful for you to define "CHEAP". Does time have no value? Are you going to take raw material , that is brass bar, tube and sheet metal to fabricate your signal bridge(s), and signals?.
You would need two bridges at least , I ken. That is because you want the operators to know their instructions prior to being at the turnouts. Are you using electric or pneumatic switch machines, or choke cables and Eschelmann Links et al ? So what are you using to throw turnouts and what is "Cheap" are in need of answering, in order to reach opening day , with respect to your matter.
Good-Luck, PJB