Squawk, that is a big assumption. Just because the aircraft is fitted with a G500 doesn't mean it is TSO for instrument ops.
Again... where does it say that you need a TSO'ed IFR capable/equipped/current aircraft to be able to conduct instrument conditions in CAVOK....? I don't believe it does. There's no need to over complicate things that really don't need to be.
You can do your instrument flying on a 7" dynon or steam gauge if you want to. In the end it's not going to matter what you did it in as it's all about competence and if you can prove to the senior instructor, CFI or ATO that you are willing and capable, you'll be ticked off with ease.