If you go with the WP-DC21, you will need to use either a fibre-optic connector to trigger your strobes (e.g. the Inon solution - http://www.inonamerica.com/products.php?product_id=272&prodcat=1&subcat=1), or to use a solution like the Ikelite manual controller (http://www.ikelite.com/web_pages/mansensors.html). The Inon solution basically gives you TTL if you want it, and manual control. The Ikelite solution does not give you TTL.
If you like the Ikelite range of strobes (I have the DS125, which I am very happy with), they you might want to consider getting the Ikelite housing for the G9, which provides you TTL with Ikelite strobes, because the housing has a bulkhead connector for the camera’s hotshoe. Also this housing allows you to use wide angle adapters if you get the short port for the housing.
Link for Ike strobes - http://www.ikelite.com/web_pages/1strobe_index.html
Link for Ike G9 housing - http://www.ikelite.com/web_pages/5can_g7.html
As for continuous LED light, these are good for focussing / modelling lights. An alternative here, is to get a strobe that has a modelling light built in. The Ike DS125 and DS200 offer this, and the Inon Z240 does as well.
Good luck!