It's not so much a question of trying to avoid deck-building because it's hard. I have been playing CCG's for nearly 20 years, and are quite used to building decks. The things I'm trying to avoid are:
1. The decks being MY decks. I don't mind playing with a deck I designed myself. But my opponents (my wife and friends) are not going to play with decks they build themselves. I want to give them a chance to play with (or against) THE Shaper deck instead of MY Shaper deck. Having build both decks myself gives me an unfair advantage.
2. I don't want to use out-of-faction cards. Mostly due to concerns about theme, but also because I don't want to use the other decks for spare parts. I like having 7 fully functional decks.
3. The starter decks seems somewhat balanced against one another. I don't want to ruin that by rebuilding the decks.
I get where you're coming from, particularly with point #1. As the only LCG/CCG player in my local player pool, I've had to struggle with this. Here's how I overcome it.
1. Expand your card pool so you can experiment. The 7 starter decks are satisfying you and your play group? Perfect - keep them as they are, and get a second core set. That, along with some expansions, will set you up to experiment.
2. To experiment with the expansions, take a starter deck from your second set, and remove a set of cards from it. That could be 1 card (Wyldside, perhaps), or 3 cards (Hedge Funds) - whatever. Replace those cards with an equal number of cards from the expansion. i.e. if the card you took out had two copies, you remove them both and you put back two copies from the expansion.
3. Be sure to stay like-for-like with regards to Faction. If you remove neutral, replace with neutral. If you remove Jinteki, replace with Jinteki etc.
I reckon that'll meet your gamer needs for new toys, will give your players the opportunity to see new cards, and won't throw the game balance out of whack, nor will it kill the themes. It'll let you tweak, but it's nowhere near the realms of full-blown deck construction.