I brought my starting Fyora to the last boss with in Geneforge 4 using an agent. It's certainly possible to utilize lower-level creations in the long term, but you might want to have more than one. Magic Shaping has the invaluable tier 2 vlish, and battle shaping has the amazing Tralls. If you want to invest in fire shapign for the long term, consider the Kyshakks.

Cryoa are not that efficient, IMO. They cost too much and there are far better creations you can get for your essence.

I kind of wanted to recommend keeping the same fyora but was rather ashamed to do it...

I did the same thing with Pokemon. In fact, I never used anyone besides the starter fire creature.