I’m a newbie, so forgive me if this sounds arrogant, but it’s not clear from your posts if you understand fundamental concepts about leasing.
Residual value is set by the manufacturer and is something you can look up on Edmunds forums, rather than having to guess at it. The dealers set the MF (but can’t go below a certain rate) and have nothing to do w/ the residual value.
You get charged a specific amount for every mile over the allowance. It’s in your contract. Dealers may “forgive” that if it’s a small overage AND you get sign lease from them. But if you go, say, 50% over your mileage, that’s going to possibly be a big, big deal.
Only you can decide what’s the most important to you, but I think that many people here would say that lowest cost for the car that you want and relative to other cars that have the same MSRP are important.
Certain cars from, say, BMW and MB have presumably inflated RV (compared to what you might be able to get in the real world if you finances the car and tried to sel it yourself) and low MF. MB also allows you to residualize prepaid mainenance (BMW includes that for free for 3 yrs/36000 mi), so you, in essence, pay for maintenance costs ever, if you keep on leasing (which saves $ because luxury cars tend to be horrifically expensive to maintain well once the warranty expires). So you save $ leasing a BMW or MB vs. owning.
And, if the car’s in good condition, the manufacturer accepts the car back and it’s on them to get rid of it.
It’s not clear why you keep talking about how easy a car will be to sell when that has nothing to do w/ you getting a lease.
If you work a lease deal and get a little lucky (depending on what car you want and the time of year you’re in the market), you can get substantially more car for your money than if you were to finance/purchase one outright.
In general, Mazdas don’t lease well compared to other manufacturers. And part of that is b/c they don’t discount their cars much (as you have discovered).
You also can’t just lease a car from a different state w/o possibly paying some heft fees (and some dealers won’t do a deal w/ you at all).