I agree with the premise but not the execution.
I'm at 97LP right now. I went in to the game with 80LP. I thought I'd get to 100... was very disappointed.
What made it worse is I had 97LP going in to my previous promos attempt! I won for 97, won to get promos, won the first promo, then lost the last 2, got put back to 80LP, won and back to 97LP.
So I had 97LP, won 2, lost 2, won 1, and back at 97LP. How do 3 wins and 2 losses result in no LP move? It's garbage... (and the one that put me on 97LP was +23, so it's not like I was deserving of demotion or anything...).
Your LP should be clearly visible and be able to go up to 150/200. So in my case what should have happened is:
97LP -> 118LP (activate promos) -> 139LP (first win) -> 118LP (second loss) -> 96LP (lost promos) -> 113LP (activate new promos).
If it somehow happens that you reach 150LP without winning a promo series (tiers 5-2, 200LP for 1 promoting to next level) you instantly promote. So let's say this happens:
99LP -> 124LP (activate promos) -> 150LP (win first promo match) -> PROMOTED. You hit 150LP so you don't need to finish your series. Makes sense since if you're earning 25-26LP per win you probably are well above your division anyways...
I just am literally sick that I was gaining 23LP per win, won 3 of 5, and ended up at the same spot on 97LP. I don't understand how it's even possible. After the first win in promos and the first loss in promos I still showed 100LP too. So I lost 20LP on the second loss, was last pick on blue side (i.e. should have been lowest MMR in the game) and only got +17...