GTA 6: 10 Things Rockstar Must AVOID From Red Dead 2
5. Accidentally Leaving Weapons Behind (On Your Horse)
The last thing you want when going into a western gunfight is realise that you've left your primary weapon on your horse.
When this happens you funnily tried to whistle your horse into battle and run after it so you can get your trusty repeater, or rifle for the battle. Even though there are plenty of enemy guns that could have be repurposed, they were never effective enough as a custom firearm. This is again due to the realism adopted by Red Dead Redemption 2.
Arthur will often get tired of carrying guns on his back and place them on his horse's saddle. So even if you do want to switch your weapon, you'd have to do it preemptively, with no notion about what is to come of the mission ahead.
This kind of quirk is something that will need to be ironed out in GTA 6 since it doesn't fit with the tone of that franchise and is plain annoying after it happens the first time in RDR2.
It would be an incredible oversight if GTA 6 managed to have this system in their game, as you could carry all weaponry holstered on your person in the previous entries.