Onboarding Friction for Volume Businesses

Anyone else hitting a wall with onboarding at the larger PSPs and even some brokers when you're moving beyond a few million a month? We've got our KYB buttoned up, but the timelines and documentation requests feel like they're still set for the guy doing five transactions a day. Specifically, has anyone found a sweet spot between the robust but slow incumbents and the nimbler, but sometimes less regulated, newer players when your flow is legitimate but high-volume? The spread and payout reliability are fine once we're in, but getting to that point is bleeding us dry in opportunity cost. What's working for you guys in terms of efficient, scalable onboarding that doesn't feel like a government audit for a simple payment rail?