How to remove validation options in Edit Mode?

I'm making a custom Form Element of "Date" type, so I'm extending "TextboxElementBox" like so...

public class DateElementBlock : TextboxElementBlock
{
    public DateElementBlock() : base() { }
}

My custom element will be 

<input type="date" />

but because I'm extending TextboxElementBlock the editor displays a few validation options...

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which are not appropriate. I did TRY and create a custom element with a custom validator, but the client side custom error message is not displayed correctly, so I figured as the browser will ensure that the "date" field will have a proper date if it has anything in it at all, so If I could remove all the validation options above except the "Required" validator then my problem would be sorted.

I tried to override the value returned by 

public override string Validators {get;set;}

inside  DateElementBlock.cs, but that only returns a list of ACTIVE validators, so it doesn't control the list of validators presented to the editors.

I think this may require a dojo solution, and I've already inspected the zip files (EPiServer.Forms.zip and EPiServer.Forms.UI.zip) and I'm hoping it works similar to adding a custom element (copy ascx/js file from zip into correct folder location). 

Anyone done anything similar in the past?