Declarative UI for components

**Hello, I'm new to public discussions like this, but have spent quite 
some time lately on web components and have some specific questions:

     1. We have no means in shadow dom to mark certain tags as optional 
based on certain property. Imagine I create <x-button> element which 
extends 'button' and my template looks like:

<template>
     <span class='ctrl-inner'>
         <span class='ctrl-icon'></span>
         <span class='ctrl-text'><content></content></span>
     </span>
</template>

         Now I wish that 'ctrl-icon' tag is optional based on value of 
let say 'icon' property of element. What is your stand on this? Is 
something like this considered and if not what you see as 'correct' way 
of handling this:
                     - Have template like posted above and in component 
code remove that tag via program code
                     - Do not have that tag in template and later add it 
via program code

     2. Are you considering some kind of 'property' binding available in 
ShadowDom next to <content> tag which will allow us to use value of 
certain property? For example imagine in sample above my web component 
exposes a property 'icon' which received value of 'icon-cancel'. Now I 
wish my rendered dom to look like:

<button>
     <span class='ctrl-inner'>
         <span class='ctrl-icon icon-cancel'></span>
         <span class='ctrl-text'>Cancel</span>
     </span>
</button>

     So I'm more or less looking for something like: <span 
class='ctrl-icon {{icon}}'></span> where similar to MDVs we probably use 
element itself as a 'model'?

     3. If I assume no property binding is available or considered, then 
I have to program UI linked to certain property manually (which is no 
problem by itself), but then what is your stand on setting this property 
via program code? If I do something like:
         elem.icon = 'icon-cancel'
     Do you thing component programmers should code that into property 
setter themselves or this should be included probably via 
MutationObserver on 'higher' level?

     Please if this is not a correct place for those questions, to 
excuse me and probably point me into suitable address. Thx in advance

     Regards Dimitar Draganov