Congrats to everyone who got IIs! I look forward to meeting some of you on interview day, and stealing your food. Feel free to post here or DM me if you have any questions, and i'll try my best to answer.
So, I actually do know quite a lot about this program and while I can't speak for what other schools are going to do, I can give you some info about what Stanford is doing.
Basically, the pre-clinical curriculum outside of the first 3-4 months of MS1 (which is a little different) is currently structured as 2 full days + 2 half days a week (although a lot of it is optional attendance and everything is recorded so your actual class-time will likely be lower). As an alternative to a research year, the option to do MS2 as a split-year was recently introduced to better support longitudinal research. For this, you do MS1 like normal, then do MS2 as 1 full day + 1 half day a week for two years, spending your remaining time on research. BWF adds a dedicated research year on top of this + more funding, extending the degree to 6 years.
Right now you apply at the end of MS1, then do MS2 as a split-year that will be funded by medscholars. I'm not sure of the actual numbers but it should be over 50% tuition from this, and financial aid or TAing (the #1 way to reduce debt here) could probably bring the real number close to 100%. The remainder of the degree will then be fully funded by a combination of BWF + the school themselves.
The program has been in the works for a while now and has been extremely well vetted - when it was in development, the school directly talked to a huge number of residency programs including basically all top tier programs to find out what their opinion would be of students opting to do this, and the response was overwhelmingly positive. The current plan is that you'll also earn a MS on top of your MD if you do it (not finalized yet so may change), and I believe they're also working on doing something to link the program to short-track residency pathways as well.
The last thing worth mentioning is that while not a sure thing, the impression i've gotten is that there shouldn't be a huge amount of issues getting into the program if it turns out its what you want to do and you apply at the end of MS1. Due to the size of the class being small (typically fixed at 90~ MD + MSTP students of which 75-80 are MD-only - the data on MSAR right now actually represents a complete outlier year), if i'm remembering correctly the plan is to have enough spots for about 10%~ of each class, and expand it based on interest. This honestly probably matches pretty well with the number of people that actually want to do something like this, especially since there's other options available if you want to focus more strongly on research too, like internally transferring to MSTP (which a ridiculously high number of people here do).