So I'm basically going to alter the way Tattoos work.
Tattoos will work basically like spell storage. You can store a spell for single use in them and then pull it out whenever you need to for zero pool cost, like a scroll. And they'll reflect the spell you have stored. Ie, Living steel dragon back tattoo will give you a sweet Yakuza style dragon tattoo on your back that can, on your command, come forth from the tattoo and attack your enemies. Or let you pull swords from tattoos on your arms.
And all the tattoos on a body part activate when the person dies or that body part is severed. So you can create Deadman switch style self destruct spells.
So theorectically you could have 10,000 dragon sigils on your arm if you drew small enough? Because a swarm of 10,000 dragons sounds awesome.