Unless I am missing something from your description, you are basically just describing using virtual hosts. In that case, I would probably set up segments such as the following (I've included a sensible SSL configuration as you've mentioned your current setup is running on port 443)
<VirtualHost _default_:443>
ServerAlias my.domain1.com
ProxyPreserveHost on
<location />
allow from all
</location>
ProxyPass /app1 http://internal01/
ProxyPassReverse /app1 http://internal01/
SSLEngine on
SSLProtocol all -SSLv2
SSLCipherSuite ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AES:RSA+3DES:HIGH:!aNULL:!MD5:!DSS
SSLHonorCipherOrder on
SSLCertificateFile /etc/pki/tls/certs/certfordomain1.crt
SSLCertificateKeyFile /etc/pki/tls/private/privatekeyfordomain1.key
SSLCertificateChainFile /etc/pki/tls/certs/chain.pem
SSLCACertificateFile /etc/pki/tls/certs/ca.pem
</VirtualHost>
and for the second host:
<VirtualHost _default_:443>
ServerAlias my.domain2.com
ProxyPreserveHost on
<location />
allow from all
</location>
ProxyPass /app1 http://internal02/
ProxyPassReverse /app1 http://internal02/
SSLEngine on
SSLProtocol all -SSLv2
SSLCipherSuite ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AES:RSA+3DES:HIGH:!aNULL:!MD5:!DSS
SSLHonorCipherOrder on
SSLCertificateFile /etc/pki/tls/certs/certfordomain2.crt
SSLCertificateKeyFile /etc/pki/tls/private/privatekeyfordomain2.key
SSLCertificateChainFile /etc/pki/tls/certs/chain.pem
SSLCACertificateFile /etc/pki/tls/certs/ca.pem
</VirtualHost>
Hope this helps!