A website similar to Localbitcoins, but with mutliple cryptocurrencies, interesting concept. P2P trading platforms are quite popular and will always be in demand, one of the alternatives if a government shuts down exchanges or bans Bitcoin, but still they are centralized with a single point of failure. There are a few decentralized exchanges Bisq, Bitshares, Waves, Decred, but not quite popular and not much support for multiple cryptocurrencies, but I do think that in the near future, decentralized exchanges would be much more in demand than P2P/OTC platforms. So just a suggestion, if you want to give something back to the community, a decentralized cryptocurrency exchange with security and privacy as priority would be better than a P2P platform. There is also Cobinhood (beta), supports around 20 cryptocurrencies with zero trading fee, projects like these would be game changers in cryptosphere.
There's still a place for a centralized exchange, decentralized exchanges are nowhere near ready to take over on a grand scale.
I think there a need for a good p2p marketplace for altcoins, it would make things so easy if you could just buy altcoins directly from someone, using your preferred payment method.
Something that's very important for me personally is that you support as much payment options as possible, just as LBC does.