If a file is so obscure that nobody has ever wanted to read it, and it was only on one node, and that node also stops serving it, then it leaves the network until someone puts it back in.
I don't understand. If you want to keep child porn available, I'm afraid you'll have to find another service. If you're writing subversive propaganda against the Erdogan regime, we're happy to keep that pinned.
You claim to pin stuff on IPFS, however you also say you comply to DMCA.
Unless you want legal trouble, this means you'll have to comply with any DMCA request that might be remotely valid.
Search up "Alex Mauer" to get a recent example of how DMCA can and will be misused.
Unless you want to get in trouble with big publishers, you will have to censor users on your service, it is essentially useless for niche files that cause legal trouble, regardless of how that is resolved.
How is your pinning service useful to keep such files online? How do you plan to defend yourself against the Erdogan or Chinese Regime?