with the right machine its possible. but i wont recomend it....
do you need all 8 inputs at the same time and do they all need to be played inside arena (effects or so?)
If you just display one live source at the time you can use a switcher and use the output to be captured by arena.
if not take a dedicated gfx mixer / seamless switcher.
Products to take a look at are:
AnalogWay LiveCore / live Premier
Arena is a playout software and i wouldnt use it as center of a big show with multiple inputs.
Laptop: XMG P507 // Intel i7-5500 / GTX-1060 / 1tb SSD / 32gb RAM // Touch OSC / Lemur/ APC-40
~self employed AV technician / Schu.VT@posteo.de