If you'd really like to use up one of your two chooseable slots for a speed buffer, I'd consider using Sakuya instead of Aya, for someone who can be a substitute tank (Or alternatively, a passable attacker, buuut), as well as speed buffer.
Also.
Rumia will most definitely play a good healer role when buffed.
Don't want to burst your bubble, but I've personally tried this, and even buffed up Rumia heals pathetically small amounts of HP until... well, Plus Disk, pretty much. She's good for healing in Plus Disk, but her heal is barely even worth CONSIDERING until around the end of the maingame. Sanae being your only healer worth mentioning is going to be a bit painful, in addition to this being an already challenging party. edit:Oh well Meiling can do a little bit I suppose. Thank god she can heal HERSELF wonderfully...
Definitely going to need to build your Mannosuke to be a second-slot tank, as well. I find him a little disappointing when built to try and be a nuker, anyway; his damage isn't terribly good.
Not only that, but there is a horrible horrible thing missing in your party, and that is DEF/MND BUFFS, which are CRUCIAL for 18F boss and help you beat 20F boss 20~30 levels earlier. And are, of course, incredibly helpful overall through the whole game. Not to mention that if you do Plus Disk then it's just cruel to attempt it without those insanely helpful buffs. Even Parallaxal at least had mag-tanky Minoriko's speedy buff, and his party overall included many highly useful characters (Who were still, indeed, underappreciated at the time.)
I would definitely highly recommend adding
someone capable of applying DEF/MND buffs. No Sanae will not come near cutting it, since she's slow, expensive, single-target, and frail. If you don't want the helpfulness Minoriko or Reimu would provide, you could at least go for Yukari, who due to Spiriting Away's massive SP cost, won't be able to do anything but DEF/MND buff and tank anyway.
edit:As for my own progress, beat SoC, found Dual Hibachi v2 pathetically wimpy (Even Kaguya is tanking the physical attacks EASILY, wtf >_>;) until they go berserk and 0hko my entire party with Dual Funeral Washing Machine. Reimu lv470 at the moment, will go and beat up Dual Hibachi v2 whenever I feel like it. It's basically Kaguya spamming Hourai Barrage until one goes down and then praying I don't get Funeral'd, anyway, with no risk until the end...