My tuppence?
10 mins to a flat battery - got to be something very wrong. In my Terrier we toured for a week without any power generation - although after the first couple of days I did handswing the engine. Got home about 20 hours later and the battery still started us! (but of course fixed gear).
If losing the stall warner is a serious design flaw then most aircraft have a whole raft of issues.
Stall warners are only added for certification purposes when there is not considered to be 'sufficient' natural buffet. What an acceptable level of buffet is has often baffled me. (Especially as differing variants of the same airframe do and don't have them and very frequently the G-reg airframes must have them but the least of the world doesn't need them). That does of course rather ignore the somewhat unnatural attitude that you need to get into to stall the thing in the first place and all those other clues like airspeed, g-loading etc. The same Terrier also had a vane stall warner - I found looking at the sky tended to give me a bit of a clue not the feeble buzzing.