Say yes to the Runes, no to the Prestige

As I explained previously, I do not agree with the introduction of prestige classes in the 5th Edition system.  The added complexity of a prestige class with the various requirements that make character creation builds that must be anticipated from level 1 is something that I would want to avoid in the 5th Edition system.

Here is my specific analysis of the Rune Magic and Rune Scribe Unearthed Arcana, with a proposition of how to change such a great magic and class concept into working with the existing 5th Edition system.  Specifically, I believe this class would function exceptionally as an Archetype of the Wizard class, as well as additional Feats for other Wizards or those who do not wish to multiclass.

Origin and Access

Rune scribe is spoken to be arcane magic of rare origin.  The Archetype of Wizard would be similarly limited in beginning the path.

Prerequisite

Using RP as a way to balance a class was tried originally, and was met with relative dismissal and players/DM's would just do this class for the "crunch".  This is an honorable attempt to keep that safeguard, but there needs to be more substance to prop up the "crunch".  By moving to a Wizard, you maintain the Intelligence of 13  requirement for multiclassing.  By moving to to a a Wizard, you keep the flavor of being Arcane based, as well as intricate patterns involved in spell casting and being a Ritual Caster.  The 5th level requirement is put the class on pacing to be equivalent as a 6th-10th level character.  So from that, scale the class by half progression, and since there is a full spellcaster progression, the balancing will take that into consideration.

Class Features

Dropping from a 1d8 to a 1d6 of a wizard does hurt the more martial classes seeking this access, but it is only a decrease of 1 average hit point.  The proficiencies of Calligrapher's supplies, Mason's tools, and Woodcarver's tools that come from the immediate class pick up will get moved to be the 2nd level Wizard Tradition Perk (passive), and the primary feat pick up that I plan.  The Feat:Skilled grants 3 skills of your choice but this is limited to tools, not actual attribute based skills. The Wizard class, just as the prestige class, offers no additional skills as well when multiclassing.

Rune Lore

This is the primary skill that allows for unlocking the "complex" functions of runes, and is the first teachings of your instructor in regards to your master rune that you need to begin the path.  This would thus be moved to 2nd level Wizard Tradition Perk (active).

Rune Magic

Rune Magic grants full caster levels, which Wizard allows for as well.  The casting levels also will grant more spell slots naturally to activate the "complex" runes, so this would need to be considered for the interaction with other full casters as well as martial classes.

Runic Discovery

Originally suggested to be 2nd, 3rd, and 5th level perks of additional runes to be accessed, I believe moving the access to the 6th level Archetype Feature for  2 additional runes at that time, with the 4th being at 10th level Archetype Feature.

Living Rune

This was to appease the delay such a class would have on the basic attribute progression.  Moving this class concept into a basic class structure removes this need, and I think it can be safely removed all together.  The awkwardness of the constant changing of attribute focus is odd from a balance perspective as well.

Rune Mastery

This augments your range of runes that can be accessed and will function in tandem with the last Runic Discovery as the 10th level Archetype Feature.  It may lack a bit of the power that other 10th level Archetype Feature may have, but this is balanced by the power of runes unlocking multiple spell like effects.

Rune Composition 
Simple-

• Passive Protective
• Cold Res/Fire Res/Breathless/Protection from Petrification
• These are passive, defensive properties
• Active Wide Command
• Icy Mantle/Extinguish Flames/Wind Step/Stand Strong
• These are dynamic, highly combat effective actions
• Active Minor Command
• Ice Form/Ignite/Self Slowfall/Echolocate
• These actions could be combat based, but are more flavorful.

Complex-

• Spell Combat Weaponization
• Ice/Fire/Howl/Crush Brands
• These cater to the martial classes, and allow them still at 5 levels into the class to use their spell slots to make the weapons have +X bonuses.
• Spell Force Expressed
• Ice/Fire/Overwhelm/Shrieking Bolts
• These actions allow for spell simulation and usage of the rune to express its force. There is an awkwardness in the wording saying you inscribe these runes onto your target, implying a touch range.  I would change this to be a range of 60' and emulate the runes of the anime Full Metal Alchemist.
• Short Rest Manifestation in Spell Form
• Sleet/Fire Damage/Meld into Stone/Levitate
• These actions replicate a non-damage spell on a short rest recharge.  The fire damage increase is an ever present factor that can really benefit a caster who focuses on fire damage, but it does mean a sacrifice in utility.  It is noticeably different than the others, but I am willing to take the trade off as balanced.

FEATS

I believe that granting aspects of this class in the form of 2 progressive feats would allow that extra flexibility to customize your character without the multiclassing hindrances in exchange for the Increased Attributes.  The precedent I would present for this would be Magic Initiate into Ritual Caster, as well as Martial Adept to give the flavor (though mitigated) of Battlemaster.

First Feat: Runic Acolyte

Req: Int 13, Dex 13, Master Rune, Teacher
Grants the ability to attune to a single Master Rune.  This does not extend attunement limitations of 3.

Gain proficiency in Arcana and the ability to activate 1 complex Rune effects per Short or Long Rest. 

Second Feat: Runic Master

Req: Runic Acolyte

Grants the ability to attune to an additional Master Rune. This does extend the attunment limitations of 3.

Gain proficiency in Calligrapher's supplies, Mason's tools, and Woodcarver's tools and the ability to activate 2 complex Rune effects per Short or Long Rest.