You can't easily interlink torrents in way that torrent clients could understand -- torrents are mostly just packages of data, not made to be a web.
On your point about the gateway -- I've co-maintained the ipfs.io gateway for the last 3 years and my perspective on its importance is the upgrade path from the existing systems. When developing and deploying new protocols, you need to onboard both users and applications/websites, and the most effective way to do so is seamless interoperability between old-web and new-web. I would imagine it tricky to get any critical mass of adoption if everyone has to choose either old-web or new-web.
But as I understand, BitTorrent can express directory structure. So the IPFS features like mounting by FUSE or browsing through web browser via local server can be implemented as the frontend of BitTorrent too.
Currently, there are tons of independently developed BitTorrent protocol implementations while IPFS has very few implementations from the same body.
You can't beat the existing software by slightly better implementations. Apart from probably IPNS, most IPFS features can be achieved by BitTorrent frontend too.
As for the gateway. If somebody want a gateway for P2P network, that's because the same P2P network is inefficient or difficult to use. If the P2P network is difficult to use, not much people run their own node. Rather, they relies on somebody else's node.
We see the bad consequence of this number of times in the crypto-currency.
In order to trust the P2P crypto-currenncy, It's essential that you run your own node for your wallet from the computer you own and trust. But the reality is, it's pretty inconvenient or difficult to do for most of the users. So what happened was, very few big central node which manage the wallet for you, exchange between different currencies for you. At this point, this is not a P2P crypto-currency. The big central node become the single point of failure. If it goes down or breached, you're doomed.
For the healthy P2P network that can replace the existing central-authority network of today, all users must run their own node and it must be very very easy to do so. So there should no demand for the gateway.
On your point about the gateway -- I've co-maintained the ipfs.io gateway for the last 3 years and my perspective on its importance is the upgrade path from the existing systems. When developing and deploying new protocols, you need to onboard both users and applications/websites, and the most effective way to do so is seamless interoperability between old-web and new-web. I would imagine it tricky to get any critical mass of adoption if everyone has to choose either old-web or new-web.