the character selection bar with the mouse becomes annoying when you create several characters, so it would be better to change it to one with arrows from left to right.

Can be annoying to apply a chemical and need to re-apply it soon after (sensexa/nul-sensexa), gas mask would be very helpful and provide breath-play

I think it would be a good idea to add an UI element that shows What interactions are available for which characters on which machine.

Kinda like the Graph in the game Breeders of the Nephelym. Basically a chart that shows the requirements for a specific action.
X would check for Penis (true/false boolean) for the player

Y would check for scale within a certain range (float value) for the player
A; B same as above but for the current selected NPC, either in the test tube or on a machine.

this would make it easier to see the "whole picture" when it comes to How much content is actually in the game.

It would also make it easier for people to do certain actions without guides or cheats.

add wooden stick

So your yiffing with a dick and you really want to do something else while porking a pussy or ass, so maybe you can record a short movement AI script and then leave it going and then maybe attach a hand/paw to something else like a breast or victims dick and fool around with that and add another short movement AI script, then when the scripts are on auto you can set the intensity of both/all at the same time or manually control more then one point  or all the points at once and tweak the mouse this way and that...

it would be cool if there was some controller support. it could be a nice touch.

Now that subjects can be inflated, I think a neat thing to do would to have a chemical that gives the user control of what body part or parts inflate before using it. 

For example, you use it on the subject, and a ui pops up showing the subject. You click on a body part, it gets highlighted to show what you've selected, then click ok. Now until the subject is given an antidote, or the chemical is used again, any form of inflation will be directed to said body part.