Workflow improvements - MKV to MP4 with EAC3/AAC 5.1 to AC3 5.1 for macOS

[theINC]

I'm looking for a way to streamline my workflow for converting MKV files with either EAC3 or AAC 5.1 audio to MP4 files with AC3 5.1 audio. The setup i'm using is streaming content from iTunes on my MBP (macOS Mojave) through my apple TV 3/Samsung dumb TV, with optical out to an old Yamaha 5.1 receiver. I've been using the following tools/process for a few years to get the desired end result, though there's a few redundant steps and multiple copies of files made along the way, that i'm hoping I can reduce:

- if the mkv has EAC3/AAC 5.1 audio, I convert to mkv w AC3 5.1 using MKVTools
- convert mkv w AC3 5.1 to MP4 using Subler
- copy mp4 to itunes library

While it's generally fast enough for my purposes, given the source mkv I can sometimes end up making the file in triplicate to get the final result. I'm working with somewhat limited space on my SSD so this can get problematic at points. Are there any new tools out that can do this all at once? Thanks in advance.