It sounds like you have built an impressive library of Flash content, which I'm sure you depend upon, so you may need to invest in your own solution.
My recommendation would be to run all Flash content via Arena 5 on a separate machine, which is dedicated
to this sole task. There are many affordable options, as you likely wouldn't need more than 2.4GHz, 8GB RAM, GTX950, which you can find for $700-800. ASUS has a laptop with 128GB SSD, 1TB HDD, 2.8GHz i7, GTX1060, 16GB RAM for $1000 US. (In case you want to be "future proof," even though this will be a Flash laptop.)
- Connect both machines to a network switch via ethernet, assign Static IPs.
- Output Arena 5 composition to Spout, use Spout to NDI (free), and capture the NDI source in Arena 6.
- Control both machines simultaneously via OSC. (They're already networked!)
If NDI gives you trouble, use a Blackmagic capture device––for a desktop, Intensity Pro 4K PCIe card (cheapest 4K solution); for a laptop, Mini Recorder (cheapest 1080p30 solution).