While gamemode loading doesn't state all the addons required, I still think this shouldn't be made just because of the silly decision of someone. If someone wants to use hacky methods they should first make sure it's practical.
You're missing the point.
You're making a new gamemode and enable 20 add-ons.
13 of those 20 add-ons use ForceRequireAdd-on.
Are you patient enough to reboot the gamemode 13 times until the gamemode stops interrupting the load?
What if add-on 4 uses the silly method I mentioned previously? Are you patient enough to check every loving addon you enabled until you find what the problem is?
My suggestion is, instead of interrupting the load on the first missing add-on, save in a text file the add-ons required by which add-on. Say, Weapon_Guns_Akimbo require Weapon_Gun. Have the load output to a text file
Weapon_Gun required by Weapon_Guns_Akimbo
and continue loading until the last add-on selected is loaded and THEN interrupt the load.