Overriding issues

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I'm struggeling with overriding core and package files on almost any level....
I have some examples....

Override \Concrete\Core\User\User
1. Created a new (duplicate) file User.php in /application/src/Concrete/User
2. Then added to bootstrap/autoload.php the following code:
$classLoader = new \Symfony\Component\ClassLoader\Psr4ClassLoader();
$classLoader->addPrefix('Application\\Concrete', DIR_APPLICATION . '/' . DIRNAME_CLASSES . '/Concrete');

3. Then added to bootstrap/app.php the following code (based on examples shown in this file):
$app->bind('\Concrete\Core\User\User', function($app, $params) {
    return new \Application\Concrete\User\User();

In my opinion this should overwrite any call to \Concrete\Core\User\User or \User, but that's not working....

So let's try something else....
In /application/config/app.php, I added a new alias.
Like this (copied from the /concrete/config/app.php):
return [
    aliases => [
        'Users' => '\Application\Concrete\User\User'
        '\Concrete\Core\User\User' => '\Application\Concrete\User\User'
In this case I thought that a call to \User will call my override, but again no joy.
The second line is also not working, although I didn't think it would....
So an "easy" override for a Src file isn't so easy... 
Performance-wise I know that reading all dirs isn't the best approche, but why not a config file-like solution like you already have for some?
And why, if you give the example in the application/bootstrap/app.php file you give an example that isn't working....
This way, by making it impossible to override, there is a big problem with updating or upgrading.
Is there another way to override my example?
Then another override thingy.....

Here I expect to overwrite any "$this->requireAsset('javascript', 'community-store');" to call my new javascript file. But it's not!
Again! This is an example from the file itself.

Overriding Elements and SinglePages is still works great, so thats good.

So I guess my bug (or request) is:

Can we make overriding of Core files easier? It's ok if its a config or an alias or something like that. But please make it possible on any level!
Every file should be overridable in an easy way. For me that is one of the great things of Concrete5!

Status: New

concrete5 Environment Information

# concrete5 Version
Core Version - 8.5.2
Version Installed - 8.5.2
Database Version - 20190925072210

# Database Information
Version: 10.4.8-MariaDB
SQL Mode:

# concrete5 Packages
Block Designer (3.3.0), Block Designer Pro (3.0.1), Cardgate Payment Method (1.2), Community Store (2.1.10), Community Store Invoice (1.1), Community Store Postcode Based Shipping (2.0), Cookies Notice (1.3.4), ExchangeCore reCAPTCHA (1.1.1), Formidable (Full Version) (2.0.8), Image Optimizer (3.2.9), Instant Page Speed Magic (1.0.5), Remote Control (1.0.2), Start Theme (1.1)

# concrete5 Overrides
blocks/search/templates/card.php, blocks/search/templates/minibox.php, blocks/search/templates/row.php, blocks/search/templates, blocks/search, blocks/image/view.php, blocks/image, blocks/pure_cookies_notice/view.php, blocks/pure_cookies_notice/controller.php, blocks/pure_cookies_notice/view.js, blocks/pure_cookies_notice, blocks/content/template/default.php, blocks/content/template, blocks/content/view.php, blocks/content, blocks/formidable/templates/bootstrap_default/view.css, blocks/formidable/templates/bootstrap_default/view.php, blocks/formidable/templates/bootstrap_default, blocks/formidable/templates/bootstrap_horizontal/view.css, blocks/formidable/templates/bootstrap_horizontal/view.php, blocks/formidable/templates/bootstrap_horizontal, blocks/formidable/templates, blocks/formidable, controllers/single_page/dashboard/reports.php, controllers/single_page/dashboard/system/permissions/files.php, controllers/single_page/dashboard/system/permissions, controllers/single_page/dashboard/system, controllers/single_page/dashboard, controllers/single_page/checkout.php, controllers/single_page, elements/system_errors.php, elements/page_controls_header.php, attributes/address/controller.php, attributes/address/country_state.js, attributes/address/form.php, attributes/address/type_form.php, attributes/address, single_pages/page_not_found.php, single_pages/page_forbidden.php, single_pages/login.php, single_pages/dashboard/system/permissions/files.php, single_pages/dashboard/system/permissions, single_pages/dashboard/system, single_pages/dashboard, single_pages/checkout.php, src/Concrete/User/User.php, src/Concrete/User, src/Concrete

# concrete5 Cache Settings
Block Cache - Off
Overrides Cache - Off
Full Page Caching - Off
Full Page Cache Lifetime - Every 6 hours (default setting).

# Server Software

# Server API

# PHP Version

# PHP Extensions
bcmath, calendar, cgi-fcgi, Core, ctype, curl, date, dom, exif, fileinfo, filter, ftp, gd, gettext, hash, iconv, imagick, intl, json, libxml, mbstring, mysqli, mysqlnd, openssl, pcre, PDO, pdo_mysql, pdo_sqlite, Phar, posix, Reflection, session, SimpleXML, soap, sockets, sodium, SPL, sqlite3, standard, tokenizer, xml, xmlreader, xmlwriter, xsl, zip, zlib

# PHP Settings
max_execution_time - 300
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - 300
max_input_vars - 5000
memory_limit - 256M
post_max_size - 64M
upload_max_filesize - 64M
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
session.cache_limiter - <i>no value</i>
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5

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