"Personally i would prefer a vault or bank style, classic."
actually the best idea is still divdiv's implementation of houses and barrels/boxes/chests :P the pack horse (even with trailer/trailer wagon) would merely be used to carry some loot/essential armaments/foodstuffs in between points while travelling like an extended version of the player's backpack...
if this idea is to be considered at all (probably for divdiv2 rather than riftrunner) then one could also consider the intelligent use of the horse in combat - say you find an encounter where there is no option to ride quickly away or you simply decide to attack, a character using a ranged weapon/attack may or may not need to get off it's horse but the drawback to that would be that the horse will be targeted for attacks as well as the player (acceptable if you're riding a feeble donkey and the party of raiders you've stumbled upon has a powerful black stallion (and you're sure you'd win the combat)... them having a horse would mean that after engaging in battle/attracting their attention there would be NO way to run away back into the travelling interface... if they have more than one horse and you're all by yourself you'd be forced to send unchosen rides running free into the wild)... thus the horse really won't add much of a tactical advantage during combat unless one adds some sort of weapon based, single-use-per-encounter "charge" attack (which would require a target be a certain distance away) for special rides (or possibly attack bonuses for ranged weapons/attacks for certain randomly encountered rare rides... - i envision attacking with nonranged weapons while on special steeds as a possibility but with negative attack bonuses (and no special move other than the distance-restricted charge attack) unless one learns some kind of "rider" skill which would negate the negative bonus... the horse could be used as somewhat of a damage sponge in that case (although still be prone to powerful chance attacks which could kill it entirely and cause travels to take weeks or months rather than days) and would also be able to run for extended periods of time without needing to slow to a trod or stop and wait for a stamina recovery...)...
just another idea i hope the divdiv team considers for any future title :P the idea of the travelling interface (for travelling in between far off cities or special locations) would mean the gamer would percieve a grand, gigantic, expansive (AND interactive - more so than instant travel teleporters) gaming world so i hope the divdiv team will see it as a viable option (it really wouldn't change the gameplay much but would add an extra layer to the game)...
EDIT: something else to consider would be the possibility of the horse kicking off it's sniping rider if ranged enemies keep hitting it from afar (and it loses 95% of it's health)... the horse would run a short distance away and the player would be able to mount it after nearby enemies are neutralized... if the player attempts to mount the horse while still being attacked the horse just MIGHT go berserk and run off into the wild (the effect could be negated by a horse tamer/rider skill - such a skill would be learned from npcs as a result of finishing a miniquest, effectively conversing, as a result of a "trick" (think the lockpick "quest" in the thieves' guild), by paying a fee or reading books)... the player must then track the horse (in travelling interface at foot speed) to get it back... that last small detail just enhances the realism and could affect gameplay by affecting quests that require traveling across long distances within a time limit...
