Are you guys ok with a smurf using that account to...

why do you need a smurf ? first, you won't have runes and masteries, so the way you play is slant (not sure this is the word, but I mean you're playing with wrong data) then you're playing again people that might not play well, again not a good way to improve. best way to improve is to play against player (and a lot if you have time), smurf is not a good option

sure you will win a lot of game at first but you might take bad habits that will cost you later on

Or you could just use a bot-lobby/co-op.

why do you need anyones opinion? i have billions of smurfs for various reasons and idc what anyone says theres nothing wrong with it

I don't personally see a problem with that. You bring a more balanced game to yourself and your teammates/opponents.

I don't mind smurfs, nor do I have any. But being advanced while playing lower newer players seem a bit unfair. Using smurf to better your orginal account, eh. Why do that, when you can practice co-op, or bots to get better with a role. I see no literal point in "I need to get better with this role, better create a new account just for this role" Makes no sense. It's really up to you, and should not care what others say.

I don't think that makes sense. Team builder gives you a separate MMR for each champion you play, why not use that for practicing new roles/champions?