First of all, competetive play definitely is on the todo list, but it is just that. Before we can even think about implementing all the customisations and support for competetive play we have to nail the core. There definitely is a plan and a design, but before we're 1000% confident in the core play it's premature to start working on these as they are so dependant on the core that when the core changes they will have to be redone.
There really are two ways of going into esport as far as I see it. One is to organically grow into it by first building a competetive clan friendly community (CS, SC, etc), the other is to pour millions of dollars into it in prize money, event coverage etc and hope it pans out (Dota 2, LoL, etc). The second method is a lot faster but unfortunately some economic constraints (unless sales at release go very ballistic) will limit what we can do with this method.
Regarding game modes, our siege (or assault might be the latest working name for it) is very similar to what you describe... We also have several other game modes we're working with, the reason for only having two at release is more about not splitting the initial player base too much, keeping it simple and allowing the community to get more involved in what kind of more game modes should be activated post release.
About making it watchable,
It might not be possible to reach SC2s watchability, (CS kinda proves that being so much longer in esports and still not coming close to neither RTS or MOBA) but it would definitely be something we'd look into improving as soon as possible when we get there. There's just so much that has to be made for UI, camera control etc etc. Livestreaming is already very possible though, I've tried that
I hope this at least somewhat clarifies our stance to the whole thing.
EDIT: We also have some quite capable competetive third person melee consultants, so there are people battling for your cause, rest assured