I love this thread. I've always wanted to try a Mana Tank AP Singed, ROA(*2?), Archangel's, Banshee's Veil, Frozen Heart or maybe a Zhonya's to replace a ROA. Plus boots, whichever. Masteries, just get the +% mana, hp regen%/mana then whatever. Runes = mana/5, ap, spell pen, whatever but mostly mana/5. I really want to try this, of course it would be ridiculous and awesome with all 6 items, but how could anyone ever afford that. Still, a fun idea.
Ok, just looked at some standard Singe builds and this seems not too far from the standard. N/M :-)