Our approach is to build on top of existing infrastructure, so no custom new language, but any language that can create a compiled output.
This does allow a lot more flexibility and computing resources to implement things, so complex things like decentralized poker can be created. pangea will be a reference dapp, smart chain.
Of course, a lot more things can go wrong if to allow arbitrary executable code. But that is another reason for having loosely coupled assetchains. Whatever code is needed for a dapp would be put into its own chain. That way, only people who care about that dapp even runs that chain and this controls bloat in a significant way in addition to limiting any damage should a dapp smart chain go DAO (DOA).
Interaction with the ecosystem will be via DEX
There wouldnt be any limit to the number of smart chains, but practically speaking you would run out of system resources or eventually network ports at some point, so people will have to limit the smart chains they run to a few hundred at a time.
Also, with the number of nodes securing a specific smart chain possibly being small, it is important that there is a mechanism like dPoW to secure such otherwise weak chains.
There's just one project and he's been working on it for the whole time. It is an ecosystem where the various parts use the functionality of each other. For example, Komodo Currencies are built on top of Komodo Platform, but yet they require the DEX layer of SuperNET to function properly. Without the "past projects" a lot of the stuff we have now would not be possible.