URL Rewrite on Windows 2016 (IIS 10) with .Net Core to point to CDN - asp.net-core

Question

I have a brand new virtual server running Windows 2016 (IIS 10). I have a website that is built with .NET Core 1.1.
I would like to rewrite all image, js, font, and css references to point to a CDN.
Problem 1, adding this rule:
<rule name="CDN Assets" stopProcessing="true">
<match url="^css/(.+)$|^images/(.+)$|^fonts/(.+)$|^js/(.+)$" ignoreCase="true" />
<action type="Rewrite" url="https://cdn.example.net/{R:0}" appendQueryString="true" />
</rule>
... results in a 404 for every request. For example a request to https://example.net/images/en-us/logo.png even though the image exists both in the real folder under and at https://cdn.example.net/images/en-us/logo.png
Is this possibly caused by .NET Core or by HTTP2 (which is introduced in IIS 10). Or do I need some sort of outbound rule also?
Problem 2, adding an outbound rule like:
<rule name="Outbound CDN: images" preCondition="IsHtml">
<match filterByTags="A, Img, Link" pattern="^/images/(.+)$" />
<action type="Rewrite" value="//cdn.example.net{R:0}" />
</rule>
<preConditions>
<preCondition name="IsHtml">
<add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html"/>
</preCondition>
</preConditions>
Causes the page response to become complete mangled unreadable garbage. Is this because of the response is sent over HTTPS?
UPDATE (2016/03/16 8:01PM MST)
Using #EricB suggestion I have tried implementing it via the Microsoft.ASPNetCore.Rewrite package to no avail.
I have this in my Startup.cs and just the local images are being loaded:
string CDNroot = Configuration["URLs:CDN"].Trim();
RewriteOptions rewriteOptions = new RewriteOptions()
.AddRewrite(#"^(css|images|fonts|js)(.+)$", CDNroot + "/$1$2", skipRemainingRules: true);
app.UseRewriter(rewriteOptions);
If I change this to:
string CDNroot = Configuration["URLs:CDN"].Trim();
RewriteOptions rewriteOptions = new RewriteOptions()
.AddRedirect(#"^(css|images|fonts|js)(.+)$", CDNroot + "/$1$2");
app.UseRewriter(rewriteOptions);
... and request an image URL it is correctly redirected to the CDN URL. But you wouldn't want a redirect, as that is adding an extra 30x response to every asset request. I am stumped why Redirect works, but Rewrite doesn't.