[Questions] Enrich any component with the serverside if or foreach expressions (namely, MVEL)

I am researching how to make a template with server side expressions that will repeat a component (foreach) or completely remove it (if). My backend parses templates with mvel.

What I am thinking is to add a couple of settings to all or some select elements. For example, to a <div> of a Cell, so it looks like this:

<div mvel-foreach="item : people" class="cell" id="iuck">
    ....some content dropped inside...@{item.lastName}... ...etc etc
</div>

Or to a Text (mvel-ending inserts separator between items):

<div mvel-ending="', '" mvel-foreach="item : people" id="iohm">@{item.lastName}</div>

After that I am planning to hack a postprocessor that will surround the repeating elements with actual mvel expressions:

@foreach{item : people}<div id="iohm">@{item.lastName}</div>@end{', '}

My dirty postprocessor will be responsible for the reverse replacement of expressions with tag attributes before loading the template into the GrapesJs editor with setComponents method.

So the question N1 is what I am missing, is there a better way to surround some select (or all) elements with server side expressions that are not actually tags?

Question N2 is how do I actually add those settings to all or some elements. I was reading the docs and decided that if I update the root component type called "default", I will add my 3 fields to all of the elements editors, so I've done this:

    var editor = grapesjs.init({
        height: '100%',
        container: editorDiv,
        showOffsets: true,

fromElement: false,
            noticeOnUnload: false,
            storageManager: false,
            plugins: ['gjs-preset-webpage'],
            canvas: {
                styles: [
                    'w3.css'
                ]
            }
        });

        const mvelModel = {
            model: {
                defaults: {
                    traits: [
                        'mvel-if',
                        'mvel-foreach',
                        'mvel-ending',
                    ]
                }
            }
        };

        editor.DomComponents.addType('default', mvelModel);

This turned out to be wrong: only the Cells in Columns in the Basic set of Blocks got updated, and my fields _replaced_ the standard setting fields instead of being _merged_, so I am obviously missing how the component types extend each other and how do I merge my traits into the components.