I couldn't catch you on Steam this morning so I'll just post here while the ideas are still fresh. From numerous 15v15 playtests ysterday:
I'm sure you're aware of the door issues with RED's 1st spawn. Also, after CP1 is taken, RED can still access the room/resupply cabinet. That should definitely be closed off after CP1 is taken.
The bend at the bottom of the curvy "Lombard St" hill is a significant chokepoint. BLU needs another path into the area. One approach would be to add an opening in this area:
... which leads out to this area:
I suspect this would shift the balance too strongly towards BLU, but in the event that that occurs, you can bring the exit down one level lower so that it's accessible to RED too. I'd start with the higher exit and take it from there.
This platform is begging for some windows to give it some actual utility. At the far end of the platform, some props are needed to block off the edge of the map:
This bend is by far the most significant chokepoint and an alternate path is needed:
This is the most obvious idea for a new path. I would recommend a one-way door at the location of the indicated "new door":
Near the final point, these beams need to be clipped to prevent RED from camping the doorway:
Also, as we discussed, I'd recommend slowing the cart down to normal speed and compensating for it with additional time (if needed).
I wasn't paying too much attention to respawn times, but I suspect work is needed there too.
Optimization is a huge concern, so I hope you can focus improving framerates as well.
Keep up the great work!