ClientPage.html

....
<form method="post" wicket:id="form">
  <wicket:container wicket:id="p1"><div class="clearfix error">
    <label for="p1" class="xlarge">label1</label>
    <div class="input"><input type="text" id="p1" class="xlarge"/></div>
  </div></wicket:container>
</form>

ClientPage.java

...
Form<Void> form = new Form<Void>("form");
FormComponentPanel p1 = new FormComponentPanel("p1", Model.of("label1"));
p1.addFormComponent(new TextField<String>(FormComponentPanel.FORM_COMPONENT_ID));
// p1.addFormComponent(new CheckBox(FormComponentPanel.FORM_COMPONENT_ID));
// ◆◆◆◆ 上記はinput要素のtype属性がcheckboxではないというエラーでNG ◆◆◆◆
form.add(p1);
...

FormComponentPanel.html

<form>
  <wicket:panel>
    <div class="clearfix" wicket:id="container">
      <label wicket:for="formComponent" for="formComponent" class="xlarge" wicket:id="formLabel">some label</label>
      <div class="input">
        <input type="text" id="formComponent" class="xlarge" wicket:id="formComponent"/>
      </div>
    </div>
  </wicket:panel>
</form>

FormComponentPanel.java

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.behavior.AttributeAppender;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.form.FormComponent;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.AbstractReadOnlyModel;
import org.apache.wicket.model.IModel;

public class FormComponentPanel extends Panel {
  
  public static final String FORM_COMPONENT_ID = "formComponent";
  
  private final WebMarkupContainer container;
  
  private FormComponent<?> formComponent;
  
  
  public FormComponentPanel(String id, IModel<String> model) {
    super(id);
    container = new WebMarkupContainer("container");
    
    // formComponentにエラーがある場合は、containerのclassにerrorを追加
    container.add(new AttributeAppender("class", new AbstractReadOnlyModel<String>() {
      
      @Override
      public String getObject() {
        if (formComponent == null) {
          throw new IllegalStateException();
        }
        return formComponent.isValid() ? "" : " error";
      }
      
    }));
    
    // label要素のfor属性にformComponentのidを設定
    container.add(new Label("formLabel", model)
      .add(new AttributeModifier("for", new AbstractReadOnlyModel<String>() {
        
        @Override
        public String getObject() {
          if (formComponent == null) {
            throw new IllegalStateException();
          }
          return formComponent.getMarkupId();
        }
      })));
    add(container);
  }
  
  public FormComponentPanel addFormComponent(FormComponent<?> formComponent) {
    if (this.formComponent != null) {
      // 複数回addは禁止
      throw new IllegalStateException();
    }
    this.formComponent = formComponent;
    container.add(formComponent);
    return this;
  }
}