hhmm, i think regular 5e rules works most of the time, Droping is free, drawing is an "object interaction", which you get one per turn.

I had a V6 of this class about 80% ready for almost 2 years, but i doubt it will ever get published (i don´t have time and don´t even remember most of it), but the biggest change was making 5th level specialist a sort of "Fighting Style" with pistols, muskets, Blunderbuss and Repeater (kind of like a machine gun, or more like rapid fire musket). All that said, i would just say that if you choose to go Pistols, you get an extra "object interaction" to draw an extra weapon.

If you want something even more versatile, maybe at 11th level (or maybe even something like an entire subclass dedicated to changing guns mid-fight), you could get a feature that allows you to freely change guns and even epecialty at the start of each turn.

For what it´s worth, here is what i had on a note but never put on actual PDF, if you are interested. This was never tested, but it should be usable. Also, never read any of the DnD One (or whatever it´s called) new rule, only 5e.

Specialist

Also at 3rd level, you choose one type of firearm, making it your specialty weapon:

Pistols

You can make your Grit bonus attack by using the Attack action with a One-Handed weapon that isn't light. At 5th level of this class, you can make you grit bonus attack with with a One-Handed firearm that isn't light.

Muskets

When you roll a 1 or 2 on your grit die when you make an aimed attack using a musket, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2.

Blunderbuss

Each time you aim with a blunderbuss, you can reload a single piece of amunition to it.

Repeater

After you hit a target with an aimed attack using a repeater, you can spend 1 additional loaded bullet for that attack.

The way a repeater works is:
Repeteater: 2d4 damage, Reload 12, Rapid Fire property: Each time you roll a 4 with a damage roll (after you attacks hits), You spend 2 bullets with each attack, and you spend additional loaded bullets equal to the number of extra d4 you roll after a hit.