Sorry, no free lunch!
First of all, what does four season mean to you?
To me it means to be able to camp in snow as well as rain and summer (read bugs) weather. That still leaves the temperature range wide open--- there is cold and then there is freeze your backside solid To get real 4-season coverage, you will probably need two sets of insulation as the sub-zero stuff will be to warm, heavy and bulky for summer use.
Simple (as in truly coordinated systems) really isn't there with hammocks yet. It is mostly a cottage industry and hammock rigs are usually a conglomeration of hammock, tarp, suspension and insulation that may be from different manufacturers. The bulk adds up. My thumbnail guesstimate has been that the lightest hammock setups are a 10oz-20oz hit over a similar ground setup. That is assuming using a CCF pad vs. an underquilt.
Budget is a major factor. You can easily drop $600 or more on a state-of-the-art kit. Are you ready for that? You can certainly do it for a lot less, but there will be compromises and it will limit the temperature range and weigh more. With both summer and winter-level insulation combinations you can drop $1000 without too much trouble. Your size and weight will have a real influence on the weight and cost of your kit.
My own 3-season kit for the Western Cascades looks like this:
Hennessy Expedition Zip
Whoopie slings, tree straps and carabiners
DIY silnylon poncho/undercover
Hennessey SuperShelter OCF insulation pad (purchased separately)
Wilderness Logics 3/4 synthetic UQ
(or all the above)
32F or 20F synthetic mummy bags
Hennessy XL Cape Tarp
Chinook Guide Tarp
Wish list: lighter stuff
Cuben fiber tarp
Lighter insulation options