You don't necessarily need to import a character to do so, the slime transform trick works for dragons too, although it takes some setup:
- Get at least two Biojuice canisters. The most reliable way to do this is to fight slimes in the brown Submission Tunnels tiles with "Transformer" in Fetish Preferences set to Always, in which 1-3 will spawn on each slime you fight. Note that you'll have to open their inventory and manually take it off of them.
- Enchant one of the canisters to turn it into a potion that turns body material to flesh. This is the only enchantment option for a biojuice canister.
- Get any random idiot to be at your mercy, such as beating up a random street idiot or chatting up one of your slaves.
- Open their inventory and feed them a biojuice canister, turning them into a slime.
- Leave that menu and command them to transform, then turn them into a dragon: past setting all of their core body parts and any desired genitals you want on them into Dragon, you'll also need to give them Dragon wings, otherwise they'll be a drake. Note that for slaves you'll need to unequip their slave collar temporarily, as by default they block self-transformations.
- Open their inventory again and feed your victim the flesh conversion potion to un-slime them. If successful, your test subject will now be a greater dragon-morph.
As a side note, you'll get a lot of corruption doing this in any meaningful quantity: using a biojuice canister on others gives you a flat 10 corruption, while the flesh conversion potion will also give a small amount if you don't have the Transformer fetish and your corruption isn't already pretty high. This is a good way to hit 100 corruption for the demon transformation once you wrap up the Dominion leg of the main quest.
If this corruption is undesirable, however, you can enchant Angel's Nectars to reduce corruption and consume them.
Also: this method works on yourself, in case you want to become a dragon.