You can remove them but they will get downloaded again on each new update.
And makes no sense to remove them: all the plugins together are less than 2MB size. So, unless you need those megabytes you're better disabling them via the plugin management system.
Or, if you want them removed, make yourself a "0" userpatch that does that. See
https://github.com/koreader/koreader...tches#overview
Half-backed solutions like the one suggested in OP give no real benefit over disabling plugins by usual means, and shall not be used.