Hi u/TheModernWizard - if you want a studio camera and already have an EF mount Sigma 18-35, you might want to consider the new Blackmagic Studio Camera 6K Pro. [Referral]

With built-in streaming, 6K resolution, 10 & 12-bit codecs, XLR inputs and built-in NDs this camera is purpose-built for video.

Here it is on the show floor at NAB: https://youtu.be/MWZdbefnHBY?t=95

A much better studio camera than any mirrorless.

Hope this is helpful and good luck with your upgrade!