Dario
Wrong.. it's because you get more DP then a level 20
For some reason your car develops faster.
Assuming maxed out Design HQ, CD and TD, as a L20 Manager
CURRENTLY you receive 20dp per race from your Design HQ and 40% research power.
As a L18 Manager you only receive 18dp per race from your Design HQ but have 46% research power.
So, for a L18 Manager to develop a car faster than a L20 they need that extra research power to equate to an average of more than 2dp per race. Design will always be affected by how other managers in the league develop their cars, but in my experience the speed of design between L18 and L20 is much the same, but the L20 has the advantage of choosing where they assign their extra 2dp per race whereas the L18 is relying on researching what others do.
Add to this the fact that a L20 Technology HQ gives slightly more Boost capacity and slightly stronger DRS and I still think the L20 has an advantage.
As an aside, it will be interesting to see what happens to research with the extra 10 levels. Unless this has been very carefully thought through I see the potential for some real issues.
Going back to the original post, I agree that low level managers promoting to Elite is a bad thing but I disagree with allowing hosts to limit the level of teams in the Elite tier. A better approach (if we have to keep the current tier system) would be to prevent promotion to Elite until a team reaches at least L16. This would prevent low level teams being matched against L20 teams and would have the added advantage of keeping teams in Pro for longer thus making the lower tiers more active.
Ultimately though, the entire league system needs a serious overhaul to ensure active players at all levels can be competitive because surely this will result in better player retention.