You said
You're under assumption that people who play ARAM also play other modes and that's just wrong.
I said
If people play only ARAM, they aren't buying champs that aren't good in ARAM. If people play other modes, that gives people a chance to test a champ and if they like it in ARAM, think "Oh maybe I should buy this to play on SR."
You said people who play ARAM don't play other modes. I accounted for this by saying if they don't play other modes, they won't buy champions with RP. If they do, they might like a champ and be influenced to buy it if they don't own it. I think you skipped an entire line somewhere as both are in there.
To summarize, when I said "Oh maybe I should buy this to play on SR" that was to a player that plays both ARAM and on SR. You are making the assumption that those who play ARAM, only play ARAM.
Who cares about the champions they don't buy?
Buying less champions removes the incentive to buy with RP as you will need less IP to complete your ARAM champion collection. You are less influenced to buy a champ if you own 10/13 compared to 10/123 because you only need three more champs, it seems like a managable hill to climb compared to the 113 you would need to complete a collection of all champs.
And what do you mean people won't put RP into secondary accounts? People most certainly do... Some of those very people responded in this thread.
People won't put the same amount of RP into secondary accounts they do into main accounts. Frankly, I don't know anyone who would buy RP on an alt or smurf, but I will leave it open that people might want to to speed the acquisition of champs up.
You're not implementing a simple solution.
It is a simple solution. Riot has done all champion free weekends once before. It would be a matter of doing the same thing, but limiting it to one map, similar to the CDR buff for URF.
You're telling Riot to give away a significant chuck of their profits.
I haven't seen proof that a majority of RP goes to purchasing champions, I would say at least 75-80% goes to skins, but I don't have any data to back that up.
Riot's simple answer is no.
As far as I know they have never commented on this issue, so they haven't answered. By bringing it up and proposing solutions, people who play ARAM hope to have their concerns addressed.