I would suggest Ashnod's Altar or Phyrexian Altar over Altar of Dementia, unless you find yourself with the ability to sac enough creatures in a turn to mill for the win. Alesha is a surprisingly mana hungry lady, my main deck is Alesha, Who is Unfinished and I have found that she needs quite a bit of juice at times.

I would suggest that you decide which route you want to take Alesha in, especially since you say your playgroup is competitive. Your list is pretty tight, I would just make a change or two. I would probably take out Mindclaw Shaman for Mesmeric Fiend. I think that if you are wanting to shut down your friends' decks, this is an option that fits with the overall feel of your deck a little better. I would also suggest putting in a Nantuko Husk so that you can have one more sacrifice outlet available to you since you have so many solid ETB effects. I like that you already have Fiend Hunter and Leonin Relic-Warder in here. I'm sure you are aware that you can permanently exile with both creatures just to bring them back to do it again, right? This would also work with Mesmeric Fiend if you choose to add it. I play my deck in a very control minded fashion, so I would also suggest cramming an Oblivion Ring and Banishing Light in here. I'm actually looking at cutting Disciple of Bolas..... I know I know, it feels like blasphemy but I find that I am wishing for a different answer when I draw him. He looks great on paper, and really is a good card in a sacrifice themed deck, but I feel he would be better in a Meren deck where you will be getting bigger creatures to sack throughout the game.

As for your maybe board I see that you have Ayli, Eternal Pilgrim. I would suggest playing her only if you are considering getting one of the most broken cards in commander: Serra Ascendant.

Anyway, I hope that my suggestions are helpful. Let me know if you want to chat more about one of my favorite commanders!

@UnleashedHavok Thanks for the feedback.

I was initially running Ashnod's Altar (and Nim Deathmantle), but I found that having a 2 mana sacrifice outlet just felt a lot better, hence Altar of Dementia. That way, you can play it on turn 2 before Alesha comes down, or on turn 4 and still have mana to activate Alesha. It's also important to note that you can (and should) target yourself with Altar of Dementia to give yourself more options in your graveyard. The fact that you can infinitely mill your opponents later on is just gravy.

My rationale for having Mindclaw Shaman over Mesmeric Fiend (or the mostly better Tidehollow Sculler) is that, while they both strip a card from your opponent's hand, Mindclaw Shaman lets you cast that powerful card for yourself. This seems much better to me in a multiplayer environment, where you need to get maximum value out of each card in your deck. It's especially useful when your meta is filled with cards like Demonic Tutor, Time Stretch, and Expropriate like mine is.

I am indeed aware of using the stack tricks for Fiend Hunter, etc. They wouldn't make the deck otherwise, because I don't want cards that are only temporary solutions since removal is so common in commander.

Serra Ascendant is something I'm considering, since I own a couple copies. Just isn't in the deck for now since my meta is so combo-oriented and the lifegain tends not to matter.