One of the biggest problems I think of with making brand lift studies more cheaper is you encourage the supplier to recruit people who answer surveys as side-income to answer questions. Places like usertesting.com are now full of "professional website testers" rather than your average customer who may be adverse to tech.
The thing about view through conversions and cross device tracking is maybe only a handful of marketing analytics professionals I know can actually measure the uplift they get from installing the required tracking from these. The first question I think people NEED to ask when investing in analytics is "will I get ROI on this or am I just making more work for myself"?
Or more often I see a brand spend money on a brand lift study when that $50k would've been better spends on more advertising.
I work in a trading desk and use a dmp daily. I definitely don't trust it 100% but there isn't really a need to. As long as I set up ~7 strategies (some of which use data from the dmp) I only care which strategy is the best, regardless of how accurate the data is. Of course more accurate is better, but that isn't something I have control over.
Sounds like we've had some similar jobs over the years!
Never had a trading job - i'm a publisher at the moment!