Frank
To answer the question if it's normal, or wanted, that low level teams can challenge high level ones: Yes, it is. As the time to level up grew way too long for players to endure to stick around to finally get into a position to start playing for real, and shorten it would make teams reach the end of the level ladder way too soon, the game underwent a shift. From grinding slowly towards competitiveness towards maintaining it during transition.
The players are given the tools to fight for wins and championships pretty much from start, what needs to grow is their experience and ability as a player to do so. However the team starts in a position of reliance and reacting, they need to find and buy a good chassis and engine from others, they need to react to the development dynamics in the league to optimize gain as their design points come from research.
They level and start into transition and things get harder, research breaks away slightly quicker than HQ points grow, at level 20 and 30 comes the decision to start an own engine and chassis, doing so hits initially hard though, not doing it means imposing a handicap on the team later.
Towards the end of the transition the team relies on its own resources, it generates most DP with HQ, is now one of the drivers to shape the development strategy, secured its own chassis and engine with self chosen strength and weakness.
However there's one point slightly out of balance. The research advantage, if played right, can be too strong, without chassis even stronger than 40 DP from HQ. The research bonus from chassis levels the field and could even shift the scales towards level 40 (needs some numbers grinding), but high levels could still use a little bit of boost, both for a little bit of advantage and keep the research game more relevant for a little bit of an extra edge for those playing it well.
Also the performance 'hole' (more like a dent) around level 30 feels a bit too deep, and wrong, to me, especially as deciding to go for own chassis and engine hit hard on their own there.
That actually is a very good summary, well done, sir.