I would have believed your position before signing Winston but now I don't know what SP is planning. TH still has not proven he can run the offense like Drew, so we will see.
Let's be fair, not many people on the planet that have ever lived can run the offense like Drew... that's why he's Drew. The offense will be different when Taysom takes over... and will have the possibility to be even more dynamic because of what Taysom brings as a threat to run or pass, and his ability to extent plays / makes plays when something breaks down and ad-lib.
The signing of Winston is for this season... There is no sense in making Taysom the #2 this year with Drew here.... It's pretty simple, if Drew has to miss a few games for any reason... You have a 2 QB system where Taysom and Winston split the duties, and you can still use Taysom is the role hew had last season... If Drew is out for the year for some reason, Taysom is your starter and Winston is your backup.