Technical Question for Using New Livestream

New to the forum and appreciative of any advice. We currently use an ATEM Television Studio (Black Magic) and input via firewire to a Macbook Pro where we use Wirecast to encode and then stream to Old Livestream. We have tried New Livestream and really like the service via their handy Broadcaster (that little red box). However, this eliminates our Macbook Pro and Wirecast encoder, as the red box becomes the endcoder and broadcaster combined. Herein lies the problem, we need to be able to have some logos, bottom thirds, and other overlays and so we really want Wirecast back. If we upgrade to the new Macbook Pro which has an HDMI port, does anyone know how to get Wirecast to output to that port so we can run it to the red box?

Here's our current:

ATEM-->HDMI-->Livestream's Red Box Broadcaster

Here's what we'd love:

ATEM-->HDMItoThunderbolt-->NewMacbookPro|Wirecast-->HDMI-->Livestream's Red Box Broadcaster

Thanks again for any help, guidance or advice you can give.