Just a thought.......
With very little effort and expense you could hang a fixture like I have noted above and also attach the shelf similarly with wall brackets. You could have this up and going in 15-30 minutes!
When you get your house remodeled if you wanted something more sophisticated you could just take off the brackets and cover the holes over with joint compound, paint and voila! Back to the old way!
A couple of additional options - you could use a couple vertical bracket mounts that have multiple adjustment slots to move the shelf and/or the light up and down. OR you could put them up without the vertical adjustment bar and just move the light up and down as you have noted with additional links of "S" hooks like I used or chain. You will probably find (as I have) that you will want particular plants lower or higher than others - and find that you are adjusting the plants up and down as well as the fixture - which can be done with small boxes, pots turned upside down, etc.