Customize Wordpress Plugin

I design book covers. I need a way for customers to edit the book cover text online and download in HD quality preserving the dpi of original images in PDF and JPG. This plugin must be exclusive to me. The site I am building will one day be multi-vendor. I have purchased a plugin that is close. I need customizations for this plugin or a new plugin based on it. The plugin has two choices for the front end style. The classic and the modern. I am using the modern because it looks like [login to view URL] which many authors are familiar with. I want to keep this UI. The modern does not work with all the plugin options. It needs to be fixed so the sizes of the images can be changed by the customer. It needs text shadow similar to photoshop. It currently has a shadow option but it only outlines the text. If the shadows could be rotated it would work fine. It needs to allow jpg downloads. It currently allows for png and pdf. But self publishing sites only allow jpgs to be uploaded. The jpgs downloads must preserve the HD dpi of the original images. I need justified text alignment added. Also need the plugin to allow copy and paste option when inputting text. It currently does not allow this. It also needs to allow image size changes. There is currently a pop up that allows this for the classic version but it does not work with the modern version. It also needs changes to the backend. I have uploaded a pdf to try and explain all the changes needed to the plugin I already own or for building a new plugin.