Ok, obviously, Ancient Tomb is plenty strong and would not be reprinted, but I'm trying to see how close we could go without it being broken.
I'm thinking along the lines of.
Tiny Tomb
Tiny Tomb comes into the battlefield tapped.
Tap: Add 2 mana to your mana pool, Tine Tomb does 1 damage to you and doesn't untap in your next untap phase.
This is obviously slower, would it still be playable or too good, or just not good enough. I would be tempted to remove the CIPT clause, but I think it just makes it stupid good then.
What about for an un-set?
Removing the CIPT,
instead:
Tiny Tomb of Doom
tap: add 1
1/2 mana to mana pool, tiny tomb of doom deals
1/2point of damage to you.
At end of turn sacrifice Tiny Tomb of Doom by ripping it in four pieces. each piece is a copy of Tiny Tomb of Doom.
Seriously though, Ilike it

i would say your original version is good but instead of "doesn't untap in your next untap phase" it should be "doesn't untap during your untap phase. You may exile a card of any color from your hand to untap Tiny Tomb."
That way it doesn't compete with City of Traitors, I don't think.