This is quite right. Security of the protocol is absolutely paramount now. Speed and, crucially, flexibility are technological challenges that will be solved. Side-chains and tree-chains will be powerful tools to help solve these challenges.
Agreed. Tree-chains is why Viacoin (which Clearinghouse runs on) hired bitcoin core dev Peter Todd.
Exactly, so the block-time*** will be rendered a moot point in the "Viacoin-versus-Bitcoin-as-a-Higher-Level-Protocol-host" debate because application specific (e.g. fast) blockchains (e.g. side-chains and tree-chains) will be rolled out as required.
Hence, all other things being equal - Bitcoin is practically a more viable host as it is (currently) more secure.
***Let's not forget that confirmation (i.e. confidence) times are more important than block-times.