If you just want to play normally, and not have to overlevel for everything, I'd recommend going for a team of 12, or at least close to it.
Team SA is a perfect fit for 12, if you include all playable characters and bosses that appear. You have Yuugi, Suika, and Nitori for physical offense, Utsuho, Marisa, and Patchy for magic, Reimu for covering most of your healing needs with Sanae filling in the rest, plus a few more random buffers/damage dealers. No dedicated tank, per se, but Yuugi can take most physical hits, and maybe you can raise Suika for MND or something, I don't know.
Team PoFV has exactly 11, not bad. You do get Komachi as a sort-of tank, but Reimu's your only healer, so maybe ATK-based Komachi will work better. Team IaMP also has 11 members, and is a more balanced party anyway, with Meiling as your tank and Remilia as backup. It's just a bit too...typical, what with everyone being often-used characters and all. Suika's the biggest oddball there.
Here's another fun idea: Team NICE HAT!
You can't just wear a hat...you have to wear an interesting or iconic hat!
Aya (fuzzball hat!)
Shikieiki (awesome judgment hat!)
Eirin (red cross hat!)
Iku (frilly oarfish hat!)
Keine (pagoda hat!)
Marisa (classic witch's hat!)
Meiling (dragon star hat!)
Minoriko (grape cluster hat!)
Mystia (winged hat!)
Suwako (come on...do I have to explain?)
Tenshi (peaches hat!)
Yuyuko (dreamcast hat!)
Or mix-and-match with whoever has your favorite hat...
It's not a bad team, as you've got both Tenshi and Meiling for tanking and Minoriko for healing (which is pretty much all you need, although Eirin's got backup heals). You've also got offensive and speed buffs, a fast paralyzer, and DEF piercing in addition to some decent physical and magical attackers.
@ NeoSerela: I've already used Kanako on my 3rd playthrough, and tried her out from the beginning of the game all the way through to the start of the Plus Disk. She's pretty decent; I'd rate her about the same as Alice, except stronger but slower for bosses. Suiga is an excellent nuke for boss fights, with a great formula and being CLD, which as mentioned earlier is very rare. She has great type coverage, too, with VoWG and a non-elemental attack. Her HP could use some work, but her defenses aren't bad.
As for the next team I'm planning, I'll probably be using Ran and Chen because, you know, 16F formula and all. And Tenshi, too, since it's been too long since I've last used her (my very 1st playthrough!). Good call on Cirno, though; I have used her for a full playthrough, but that was on a party with no offensive buffers. Can Iku turn her into a half-way decent attacker? Who knows?