I want to be able to input a WeChat user id and somehow be able to generate the corresponding WeChat QR code on the screen.. is this possible and if so how do you do it?
Unfortunately, you can't.
3 years ago, you can generate QR code from URL: http://open.weixin.qq.com/qr/code/?username=<wechat_id>. However, this API is unavailable now. It seems Tencent disabled this interface due to security consideration -- this API can be easily abused to send spam invitation.
If you speak Chinese, please check https://www.zhihu.com/question/21384291 for discussion on this topic in history.