Alright, there are a lot of good suggestions in that post, ELW! I'll elaborate on what I've considered in your post below.
Arcane Sanctum is a good, lower cost means to get the colours I was wanting instead of Godless Shrine or the Caves of Koilos. I don't like the Sanctum comes into play tapped because of late game issues, but I could use a Lair that has those colours instead from Invasion. I could any combination of the three in and fix my minor colour woes right there by removing the Swamps.
For Oblivion Ring, that's a feasible answer that I will indeed do. I didn't think of that one when I put Unmake in there, and Oblivion Ring would prove superior due to versatility.
As to the Advocates, I admit I was probably casting a blind eye their way. They were some of the first Angels I managed to get a hold of to start my Angel collection. But you're right, they tend to be underpowered and typically I hoped for a bigger draw. Pristine Angel would make a good blocker, I'll put her in. I don't have an Adarkar Valkyrie yet, but I didn't realize their price was so low now. The last time I checked they still had a pretty hefty pricetag. I'll be sure to grab one or two of those as well. Ditton on Blinding Angel, the shops I regularly go to didn't have any in stock for the last year and no one would trade any. I always watch for them though. I could toss in a Platinum Angel and a Pristine Angel as replacements. That should cause some major problems for the opponent. I have another Serra Angel or Seraph to use as well.
Desolation Angel didn't work in this deck as good as one might think. The permanents I have are higher costs so I don't get as many out. Killing my land has proven a disadvantage for me more than once, particularly in Multiplayer where you'll garner a lot of hate. Herald of Serra is another I'm after, but the Echo is a pain. I really only use the Karmic Guides as chump blockers and as a flying Breath of Life. I rarely pay their Echo Cost. Instead I just play another Karmic Guide to fetch a Karmic Guide to fetch another Angel. Gives me more chump blockers in case I need them. Toss in Reya for lots of Angel revival goodness here.
As to mana acceleration: I agree with the Dark Rituals being bad due to loss in card advantage. I use them frequently to throw an Urza's Incubator and/or Gilded Lotus into play to speed up the deck overall. Unfortunately I do not have any Worn Powerstones or Coalition Relics. The relics are an awesome idea though that I'll have to try to get a hold of. Dark Rituals are basically only good if I have the other artifacts in my hand early game:
Turn 1: Swamp, DR, DR, Gilded Lotus, Urza's Incubator (5 cards used)
Turn 2: Swamp or Plains, Tap Gilded for White and play an Angel that is 7 CMC or less.
Do you figure Orzhov Signets would be a feasible substitute? It's another way to fix my mana and does give reusable minor mana acceleration. I'll miss the Turn 2 Serra Angel by removing Dark Rituals but I'm pretty sure I can do without that as most Multiplayer decks aren't rolling yet. I could do something like Sisay's Ring as I have a couple of those and 4 Orzhov Signets. I have some Spectral Lanterns as well.
What do you folks figure would work best in that situation?