I agree with some of your suggestions (more IP, skin tab, in-game setting in client) those are things that honestly should have been done years ago and it's sad they haven't been done. I get wanting it to take time to buy everything, it's a free game and they want you to buy RP. However, I've been playing almost two years, I've spent hundreds on champions (and hundreds on skins) and I'm still missing most of the runes and 21 champions. That's ridiculous, just because I don't play every day doesn't mean I shouldn't have access to things like runes and champions.
More specifically: skins are mostly ok but I'd rather if the base prices were slightly lower and the sales were slightly less of a discount. Making that compromise so that sale prices are similar but non-sale is slightly lower would increase overall sales. Champions RP cost should be significantly reduced, 975 for a champion is absurd and the discount for 4800 and lower isn't nearly enough. 4800 is 76% of 6300 but 880 is 90% of 975. Cutting champion RP costs in half and then making sales 25% off for champions would be a much better target and would leave IP more flexible for runes.
I do disagree with some of your points: competitive champion pool and bans. First, the champion pool viable in solo queue is HUGE, you can play virtually anyone to diamond, so I don't know what your complaint is. Second, you can't balance a huge pool for competitive play where the kits themselves largely determine usefulness without making every champion clones of each other. Riot does a really good job of making different champs viable. If you look at LCS picks alone (no Korea or Asian leagues) at one point over a split and a half (spring and half of summer season 3) over 85 unique champions saw play in NA and EU. I haven't made a spreadsheet recently but I'd guess s4 was similar. Champions largely depend on team comp, since you can't restrict team comps you can't predict how the meta will shift until it happens.
As for bans: 6 is enough, you can't do more because it would allow entire roles to be banned out. You already stretch things in competitive when you see 5 mids or jungles banned, how can you possibly expect people to master upwards of 8 champions at all times? Solo queue would be even worse, sounds great when you think about banning other people's champs, but how will you feel when 6 bans or more are all YOUR role. Or how about when two people on your team say: all my champs are banned, I can only mid as Fizz...