You've nailed one point there, there needs to be more variation in the events, given the vast pool of stage/condition combos, it's disappointing that it doesn't vary. Also, there needs to be an option for realistic length, like WRC Generations by KT had, could have as many as 18 stages in an event and it felt like a real WRC challenge. I know it wouldn't be for everyone but it's a shame there isn't an option for it.
Then there's the structure, the calendar structure is a good idea but it's so poorly executed, forcing you to skip events thay you need to complete because of schedule clashes, needless roster events or garage expansion stuff, just so cluttered and unnecessary. If they want you to do multiple championships in a season, it should do it in a way that deliberately keeps them apart so you can do it instead of sticking to the same calendar season after season with all the championships available crammed into it.
I'd do it one of two ways. First way would be to imitate the F1 games, merge the concept of MyDriver and MyTeam together and focus on the WRC. So upgrading facilities, car performance/R&D, occasional invitational events but the core focus being the WRC. Like the F1 games you can choose where to start, JWRC, WRC2 or WRC. But then also the choice of whether we start our own team or drive for existing teams. Then at the end of each season we can either sign for a new team/promote up or create our own team/car. With more of a focus on WRC they could then implement more realatic elements such as choosing what rounds to compete in for the WRC2 campaign, perhaps being signed by a WRC team as a 3rd driver and running a part time campaign before signing a full season. Just really hone in in the WRC experience and make it as realistic as possible.
Option 2. If they insist on sticking with a calendar format and having chances to run multiple classes of car, then it needs to ensure clashes don't happen otherwise it's pointless. Structure the WRC events and slot the 2nd championship within that. Drop the benefactor stuff, let us buy and keep cars so we don't have to get rid of them to afford the new seasons cars.
For me, going towards the F1 style career mode is preferable. Then they can give us a really robust and content rich championship mode or historic mode alongside career. For this mode they could lean on Colin McRae Rally 2005 as a template. A pyramid of championships starting in slower cars and working up, adding difficulty and longer events as you progress. This would also then justify adding new historic cars and perhaps even non WRC locations.
