It isn't actually that big of a change, .
He already summons 4 units from Ered luin/ Erebor.
It would just be nice if you could choose what units you summoned
Well, I must explain you few things.
As LordDainIronfoot said earlier there is difference between dwarven lord and king.
I say there is
BIG difference.
Lord as title exists from first age, there was seven realms and seven dwarven lords. They were all equal among themselves. Durin was most famous LORD. He was Lord of Longbeards clan, not King.
About title KING, maybe it was used for Durin as King of Khazad-dûm in first age because he has founded realm of Khazad-dûm (can't be precise about that, I presume that I have read it somewhere) but this title became reqular with foundation of Erebor kingdom and specialy with discovery of Arkenstone.
Simply Thrór was King Under the Mountain and possesion of Arkenstone gave him right to call armies of all seven realms to his aid. Simply dwarven realms pledged loyalty to the Lord who possesed Arkenstone (Why? I don't know, but this made nice hierarchy amoung Dwarven Clans/Realms). This is principal analasys, plese don't go into details. So we could say there is one King (High Lord) of Dwarves in third age and others are still Lords in their realms. That title King is connected with Erebor like its seat of power, and Durin's descendants (clan Longbeards) are in possesion of that title (Simply this happened with Durins line, it was luck in discovery of that Stone). Later Dain inherit this title from Thorin II Oakenshield as closest alive member of Durin line, and dwarves simply don't change this type of hierarchy until end of their time. So Dain become King under Mountain.
So there is big difference (In ruling power) between Lord Dain II Ironfoot and King Dain under the Mountain. That justifies King Dain ability to summon barracks and call to arms any of seven (
In my opinion there is no seven dwarven realms in third age, because Belegost and Nogrod have been destroyed at end of first age and survivors of that clans went to Khazad dûm, later from was exodus from Khazad dûm to Gray Mountains, then from Gray Mountains to Erebor. After arrival of Smaug they fleed from Erebor back to Blue Mountains (ruins of Belegost) and later they reclaim Erebor, for more informations simply read one of these: Lotr Wiki or Tolkien Gateway) dwarven realms (in game we have three possibility ofc). About Lord Dain II Ironfoot, he is at first place LORD of Iron Hills and there lies his jurisdiction, because of that I am
HARDCORE follower of idea to replace that summon power at level 10 with Ram summoning or someother IronHills units, becasuse he don't have that ruling power to call others dwarven realms to his aid (simply he hadn't global ruling power at that point of time, maybe some clans will come to help him, but take some informations into consideration, like why he (Dain II Ironfoot) didn't help Thorin with his quest (they were kin, and he refuses to help, simply Thorin didn't have global ruling power) and there is also some ancient brawl between Longbeards and Ironfists (Clan from Red Mountains), so this is one more reason)
Those reasons simply justify possibility of making new summon power for Dain.
So current summon spell is more than enogh (It is agains Lore facts!!!) and you complain about units upgrade and units choise. C'Mon!
And, King Dain of Erebor's summon is better than the Iron hills one.
Why?
1: It is another barracks (Huge adavantage)
2:You get a-lot of unit diversity with this barracks, and you can choose whatever unit from whatever realm you want.
3: A funny thing is, this barracks has a habit of shooting arrows once you get it
So, it can act as a tower,a second/third barracks,and unlike Iron hills Dain's summon, you can consistently hire dwarves from other kingdoms.
And if you got a level 10 Dain, you won't mind the extra resources.
Another thing, (Iron hills) Dain does not summon fully upgraded infantry, so you still have to pay for that.
The team should probably change his name to Lord Dain or Dain Ironfoot; Or should I say Dain ironHead
There is no reason to reapeat facts I wrote above, simply this is too much for DainIronfoot already, and don't compare King Dain and Lord Dain Ironfoot and theirs abilities.