So seeing as RDM currently is a very straightforward proc-based, build up and spend style of play right now, there's a couple paths I can see them going for in the future, increased support (kind of boring but que sera sera) or hopefully increased complexity (more room for optimizing damage etc. etc.).
Now personally I wouldn't mind juggling a minor maintenance buff of some sort, other people have mentioned additional mana spenders which could also be interesting as a primer spender that leads up to the main combo or a high damage nuke with a moderate cooldown (Ardor basically). That said I'll put forth what I think would be interesting for the former two.
Acceleration Cascade (Maintenance buff): Each time you consume Dualcast with a damaging spell or use an Enchanted Weaponskill you gain a stack of Acceleration Cascade, increasing your spellspeed by 2% for 10 seconds stacking up to 5 times. Casting Verholy or Verflare doubles the effect of each stack for the next 10-20 seconds. Acceleration Cascade can only be generated from Vercure once every 5 seconds. This is a trait
Chainspell (Primer spender): Consume all of your mana, gaining Chainspell for 1 second per 10 mana points consumed (would be subject to change). Chainspell grants instant casts for damaging spells for its duration and reduces your GCD by 1.5 seconds. The idea here would be to generate enough mana that using Chainspell would allow you to cast Veraero/thunder enough to get you back to the main combo, might have to have it reduce the potency of them by a slight amount. This ability would probably need a modest recast. Note this specifically affects damaging spells because being able to Verraise or Vercure every second for up to 20 seconds would be absolutely bananas. And I don't like bananas.
--This one isn't necessarily in any of the categories I mentioned but I thought it might be interesting--
Applied Discipline: For the next 15 seconds your Enchanted Weaponskills do not cost mana, but their damage is reduced by 20%. For 15 seconds after that, Verthunder and Veraero have their cast times reduced by 80% but do 15% less damage and do not proc Dualcast (the GCD would artificially be reduced down to whatever Verthunder/aero cast time would be, but only if one of those two were cast). The theme here would be that the Red Mage temporarily focuses on only one side of their power for a short duration. Needs more polish to be sure but thought it would be an interesting concept. Additionally you could have them last 20 seconds but whichever discipline you get is determined by what mana is higher at the time. (White for weaponskills, Black for spells and you only get one.)
Constructive criticism, thoughts, alternative suggestions on the topic are all welcome. Destructive criticism while not welcome will still be considered.
Edit: If you're at least reading the OP instead of just responding to the title, if your response is somewhere along the lines of, "I wouldn't make it complex I like it simple because X," or the also popular, "There are other complex jobs why'd you pick this one," please move on, it's already been covered.