Looking back through some notes on sample builds
The issue with the cohort became the ECL17 cap pre-epic. Improved Cohort doesn't really help unless your leadership score sucks, and Dragon Cohort was explicitly limited to the table (unless DM approves otherwise I suppose).
What I was inevitably looking for was retaining the Cleric list, and thus avoiding the Sovereign Archetype while fitting in War Weaver 5 and Spellguard4 in order to weave personal spells. Barring Legacy Champion tricks. Mindbender/Mindsight for general scouting.
The options for Draconic Auras and Dragon Pacts also are somewhat interesting options as well.
ECL20
Wyrmlings (Small)
Vanilla build
LA2 HD4 Wyrmling Steel Dragon / Sorcerer 5 / War Weaver 5 / SpellGuard 4
Caster Level 14th, 7th level spells
Flaws, Versatile-Heighten Early Entry, Practiced Spellcaster
LA2 HD4 Steel Dragon / Sorcerer 2 / MindBender 1 / War Weaver 5 / SpellGuard 4 / Arcane 2
Caster Level 14th, 7th level spells
LA-buyoff, Flaws, Versatile-Heighten Early Entry, Practiced Spellcaster
LA2(buyoff) HD4 Steel Dragon / Sorcerer 2 / MindBender 1 / War Weaver 5 / SpellGuard 4 / Arcane 4
Caster Level 16th, 8th level spells
Young (Medium, riding)
Versatile-Heighten Early Entry
LA4 HD10 Young Steel Dragon / War Weaver 5 / Arcane 1
LA-buyoff, Versatile-Heighten Early Entry
LA3(buyoff) LA1 HD10 Young Steel Dragon / War Weaver 5 / Spellguard 4