hmm, will start with the Saturn
Sega doesnt release the 32x and Knuckles Chaotix is a launch title
No Sega of America/ Sega of Japan feuding
Sega of America doesnt kill the Saturn when they told the press, the Saturn was not the future
On a software note, release sonic x-treme and more importantly money hat enix for a exclusive Dragon Quest bundled with the graphics enhancer plus
maybe money hatting Konami
And most importantly no stealth release as otl
Does N64 and Gamecube count from a financial perspective and marketshare disaster?
Will do them anyways
Gamecube
Goal at least 33 million (same as n64)
OTL sales 21.74 million
A few ideas
Lets start with Nintendo manages to retain Rareware buy purchasing an extra 2% of stock, thus securing Banjo, Conker, Perfect Dark etc
This should enhance it by at least 5 million sales as less market share loss to Microsoft and less drought with Donkey Kong Racing, Banjo 3 and a good Perfect Dark Zero
So were at roughly 27 million with that
Next phase, Sega accepts Nintendo's bid to acquire them in 2000 while before the Gamecube's release mainly effects the Gamecube as the Dreamcast dies as otl if not earlier and begins working on gamecube launch titles (interestingly the gamecube and xbox could run Dreamcast code which partially explains why Sega went nuts with ports to both systems in otl)
So Shenmue II is never released on the Dreamcast or is Crazy Taxi 2 and are both Gamecube exclusives as is Fighting Vipers 2, Sonic Adventure 2 is a Gamecube launch title.
Lets say 80% of the sega Dreamcast owners eventually get a gamecube 8 million more, plus less lost marketshare to Microsoft and Sony
So at least 35 million sales with this and in theory if the gamecube had a regular disk drive and not mini discs it is feasible Dreamcast backwards compatibility could get worked in if the pod is in 2000
With bigger discs or dual layer discs like wii, can hopefully get Namco to make Xenosaga multiplat and with Nintendo in arcades could try and persuade them to get some more support for it and possibly some more support from Square Enix
Nintendo 64
Easy have the 64 DD be bundled at launch and have FFVII stay a Nintendo exclusive, this should lead to Mother 3 remaining on the 64 and staggering loss of Japanese marketshare is much less with Square staying with Nintendo.
The CD32 never stood a chance IOTL as Commodore went bankrupt less than a year after its release. If Commodore had more secure assets maybe they could have figured out the right formula after the CDTV and CD32 to re-introduce the Amiga OS and chipset into TV rooms. 
