It's not going much, honestly. In the demo version I extended the level length about 20x, had larger hit boxes, fast and dangerous attacks, and stats that affected random comments she would make. Damage was only suffered on orgasm (of either party) and enemies were reworked to have a lot of stamina they could slow to regenerate or go fast to disable your escape. In testing, escape could be easy or you might be unlucky and end up struggling through multiples. Added voice to her too, though that's been added officially since.
The game's much more convoluted now. Although I was able to adjust it so health, clothing lost, etc are all preserved from level to level, I had issues figuring out where the control for the sentinel tentacle wall went, how to take full control of the ESCAPE! popup, etc. What worked in the demo doesn't work now, basically. For the most part, though, I'm holding off on making a full revamp until the game seems completed (second boss would be nice)... so most of my tinkering is refreshing my Flash skills (been years), learning all the hooks of the game, and testing different engine-changing things.
The general plot I gave the demo was that a newbie adventurer witch accepted a quest to investigate some evil magic affecting the animals of that forest. She finds the forest has a curse that amplifies female pheromones and drives the inhabitants to uncontrolled lust. She enchants her underwear with protective spells to nullify the curse's effect on her and sneaks into the forest to investigate. Once deep in, she realizes her enchantment was somehow nullified by the powerful curse, and it erased her panties along with it (she starts without them, thus completely vulnerable if caught). She has to flee the forest, preferably before she's given an introductory lesson in sex. In the full game, she'd be forced to flee deeper into the forest, most likely losing most of her clothes along the way and gaining a lot of unwanted experience before defeating the succubus causing it.
One concept I had (though I've not worked out yet) is to have clothing play a big role. For example, when caught she may instantly escape the enemy (no rape) by tearing away (and losing a piece of clothing).
If this doesn't succeed (affects the ending already, though she convinces herself it's not human so it doesn't count) and they start their attack, she can attempt an escape as normal. On completion of the bar, the enemy tries to grab her in some random place. Say they grab for her waist. If she has her skirt, it tears off and she escapes. If she's lost it already? Maybe a 90% probability they grab her hips and she has to try again. Or, losing hat or getting her hear grabbed, etc.
Once it comes down to being stripped completely in the later levels, there'd be no guarantee you can escape in any reasonable amount of time, and orgasms reset the bar (something she didn't want to experience yet)... which makes the enemy completing their attack more likely (having received a load notably upsets her at the end... much more so if it resulted in pregnancy). Then again, there's also embarrassment if she returns to town without her little vest or her skirt (she's got no panties, afterall), so you'd be bound to get some sort of ending of her completely mortified about what happened.