Suggested

XP for buying items in store

Maybe 100 xp for every euro spent for example? Maybe be an incentive for people that aren’t maxed out to make purchases rather than just waiting for months to be competitive?

You can already spend money on XP boosters.

That cuts down the progression time in half and you can only have one active at a time. It takes 1 month to get from 25 to 26, assuming you watch the 3 ads and do 2 quick races each day. 2 weeks if you have the booster. Once you’re in elite, you’re not competitive until you have design and technology buildings maxed out, what are we talking about here?

I agree completely. I don't fully oppose the suggestion - I'm just saying that this feature sort of already exists.

This won't happen as covered in the recent blog, real currency will be used mostly for aesthetics. 

Also I would stop playing iGP if they allowed us to "buy" Exp as this would undermine everyone's efforts that has been made before. This game is a slow burn. Why would you skip the game by jumping to max level as soon as possible?

Beaten tonnes of Level 30 Teams as a level 23-26. The difference you have between 20-30 bracket is normally decided by Racing Strategy, Race Management and Driver Management. The benefit you gain from Levels between 20-30 aren't that huge.

So have I, but if you’re in a competitive league with a lot of 30s, they will have all aspects on point (good drivers, maxed out buildings, good engine and be active during the race). I’m now lvl 25 and while I can make some kind of an  impact in the beginning of the season, as the design points difference starts to accumulate, I just can’t compete (and there’s only so much I can grow my driver, even if he’s talent 30, if I’m level 25).
The problem is that a 10 lvls gap per league division is too big (and no, it doesn't matter if it’s at pro or elite or whatever). I would (here we go again with us doing someone else’s job, never gets old 😂) redesign the leagues to a +/-3 levels compared to you. Does it take a lot of thinking and coding? Perhaps. Would it make things more interesting for the players and perhaps generate more revenue? I would say so.
With this mechanism you don’t need to create an xp purchasing feature, there, solved that problem too :)