You need runes to fill those rune pages which means spending even more IP on runes early, so I really don't like this idea. Spending IP on those runes sets you back on spending it on champions.
Plus two well made rune pages is all you need for a REALLY long time, certainly for new players, which often have no clue what to do with 2 rune pages let alone 5. As for smurfs, most smurfs are far more directed, they are made for specific reasons and they have better directed rune pages. Yes from a min-maxing stand point they are not going to be perfect, but even with 5 rune pages you will run into similar issues. Even from a min-maxing standpoint there is rarely a true best relative to play style and item builds. For instance AD vs armor pen is going to be extremely situational. Or armor vs health vs mr.
Basically you could fill 10 rune pages just to try and play a set of ADC's optimally, that is a lot of IP. Or you could fill 1 rune page to play pretty much any ADC slightly below optimally but you have all all of the ADC's unlocked. The same can be said for ANY position in the game.
Actually I would say adding rune pages is such a bad idea that I could see Riot doing it. It would get players to dump more IP into runes leaving them with fewer champions to play which they would have to purchase.
Personally the changes I would like to see are:
Runes:
Have Tier 3 runes purchasable from level 1.
Give more information to players as they level up, giving them some direction to building the rune pages as far as what are the most common rune choices for each slots, but still giving the player options. For instance when the first red rune is opened inform the player that these runes are usually offensive. For example AD/ArP are the common ones for AD champions. Yellow tends to be more defensive with health/armor...etc.
Let new players know that they can use IP to purchase champions as well, but since runes can only be purchased with IP it would be a good idea to at least fill the available rune slots and if they have left over IP after buying the runes that can go towards buying a new champion.
Champions: With the number of champions now implemented this really needs to be changed. To give both new players (and new accounts in general) a boost.
Give new players the free week champions from the week prior to own. This means players would have 20 champions available to them in the first week. This is really important for new players as it gives them options to keep their interest when exploring the game. Plus now that there are 123 champions new players (or even accounts) really could use a boost in initial champions.
Every 5 levels give them a random champion from the free pool. This would 16 total champions for free. Add in 5-10 champions they could buy with excess IP, players can comfortably move into ranked games if they want.
Riot is at the point where they need to give new players enough options to keep their interest. Most new players will have been exposed to LoL in some form but may be missing out on some of the nuances (such as buying runes) give them a little more information so they can responsibly buy runes from the get go. Provide them with enough champions that they can find one that they love and will keep them playing the game.