Is it possible for DSPs to use their current sophisticated server side bidding funnel to evaluate and send the ad-candidates as part of perBuyerSignal to be used for on-device auctions? And finally, during on-device auctions, one can think about doing an intersection of the ads defined at the IG and ads candidate returned via perBuyerSignal to finally select an ad?

This approach can help DSPs to reuse their current server side filtering logic otherwise the DSPs will have to port a lot of their bidding logic on the client side.