DMs have a lot of things to deal with, it's a big server, and they're not always going to be inclined to help a player with such a minor request. May as well give players the ability to enable summon RP themselves, since it isn't like you're actually asking for a drastic change (like modifying a spell to set things on fire).
I'm not sure how much of a drastic change it would be. I know that the "don't start summon duration until combat starts" idea was suggested... years ago I think? I figured that the reason why it hasn't been implemented is because it's something that's hard to implement. (since it'd require some custom scripting at the least I'd think?)
Also, you have to consider the added power that such a change would make. One of the biggest fears of a mage is to be caught unprepared. It's a lot harder to surprise a mage when they have a summoned guardian who basically lasts forever until combat starts. I know I'd sure as hell think twice before attacking someone if they were constantly followed by a hound archon.
If you want to do some custom rp with a summon, it should be a significant scene for your character and preferably others as well. If you're planning such a significant scene, get a DM to help. Wanting to make your short term combat summon last long longer for rp reasons is... kinda cheesy. It'd be like a cleric asking for divine power to last until combat started, so they have more time to rp with the massive str it grants. Part of the downside of short duration spells is that they have a
short duration. You don't have time to stand around and flex while you're using divine power; you cast it, beat some things to death, and then it runs out.
And if you want to do spur of the moment rp with the summons, then try to work around their short duration.
Summon a dire wolf, then emote:
*The snarling wolf leaps at McBadGuy. Just before it makes contact, McWizard snaps his fingers, and the beast disappears*
Then unsummon the wolf.
^You've effectively threatened McBadGuy with your summon, and it didn't require any extra dev/DM work to make it happen.