Well, a passive repeater is -- surprise -- passive. Like a resistor or capacitor are passive cmponents. No amplification, and no power source. So an access point does not qualify to the title. It would be an active repeater. And it needs power feed as well, adding to the complications and expenses.
If you try to beam through the woods, I would try with horisontal polarization, use two good, directional high-gain antennas, and aim with a map and a compass. But, even if you some bright and dry day get the link up, it does not mean that it will work on a rainy day. Wet trees absorb signals on this band pretty well!
I think the link through/around the forest should be a dedicated point-to-point link, and it would be better to keep the omnidirectional antenna separate from that PTP link. Maybe using two access points, one for local needs and other for the "difficult link"?
If you can find that somebody's tower is visible from both buildings, try to use it as a passive repeater with two high-gain antennas. One does not need to talk with the owner in the first place--I don't think it is trespassing to beam the construction for a technical test
I think your boss might sign the purchase order for some antennas and cables to test it if there is some hope for a simple solution.