How could I deep Customized the element ui ? #69

Our team need to deep customized the ui, such as: use underlines instead of frames for the form, move icon or text position or size in some components, or add more icons.And maybe add more custom components
element-theme looks not customized enough for our team. Is there a best practice for this kinds of demands? Thanks.

我们团队里需要更加深度的定制element的ui内容，比如在表单里用下划线代替方框，移动icon和文字的位置、尺寸，或者增加更多的icon等。还有可能增加一些自定义的组件。element-theme看起来好像并不能有足够的自定义空间，对于我们团队这样的需求，请问是否有什么最佳实践方案呢？谢谢