I went to B&H and did a search for all the M4/3 lenses and came up with 18 different lenses that appear to be within reach for use with the X5/X5R. There were a bunch more that were too heavy or to long or both. There are lenses from Panasonic (8), Olympus (6),Rokinn (1), and Sigma (3) with FL's ranging from 7.5mm on up to 100mm. I limited the weight to 200g and lens length to 60mm. I don't know that all of these are adaptable but here's my list:
1. Panasonic 20mm f/1.7, $268, 46mm filter, 87g, 25.5mm long
2. Olympus 25mm f/1.8, $299, 46mm filter, 136g, 41mm long
3. Olympus 45mm f/1.8, $299, 37mm filter, 116g, 46mm long
4. Olympus 14-42mm f/3.5-5.6, $199, 37mm filter, 91g, 23mm long
5. Panasonic 42.5mm f/1.7, $348, 37mm filter, 130g, 50mm long
6. Olympus 12mm f/2.0, $649, 46mm filter, 130g, 43mm long
7. Olympus 17mm f/1.8, $399, 46mm filter, 120g, 36mm long
8. Panasonic 14mm f/2.5, $268, 46mm filter, 55g, 21mm long
9, Panasonic 14-45mm f/3.5-5.6, $268, 52mm filter, 195g, 60mm long
10. Panasonic 15mm f/1.7, $528, 46mm filter, 115g, 36mm long
11. Panasonic 25mm f/1.4, $598, 46mm filter, 200g, 55mm long
12. Sigma 60mm f/2.8, $209, 46mm filter, 190g, 56mm long
13. Panasonic 35-100mm f/4-5.6, $398, 46mm filter, 135g, 50mm long
14. Sigma 19mm f/2.8, $169, 46mm filter, 154g, 46mm long
15. Sigma 30mm f/2.8, $199, 46mm filter, 143g, 41mm long
16. Rokinon 7.5mm f/3.5 fisheye, $239, no filter, 197g, 48mm long
17. Olympus 9-18mm f/4-5.6, $549, 52mm filter, 155g, 49.5mm long
18. Panasonic 8mm f/3.5 fisheye, $640, 22mm rear filter, 165g, 52mm long
Again, I don't know that all these lenses will work properly, but they appear to be within the ballpark of weight and length. Since it looks like the main limitation is the ability to balance the gimbals I think the lenses listed above cover all the possible lenses but it's also likely that some will not work. The dimensions listed include the lens length because two lenses of the same weight will not balance the same if one of the lenses is longer than the other.
If the 35-100mm lens works that would give the longest reach and would make it possible to provide close up shots at greater range. The next longest lens is the Sigma 60mm.
I note with interest that 46mm is by far the most common filter size. The addition of a filter will affect the balance and it's for that reason I indicated that when a lens is adapted and made to work the balancing weights, if any, would also need to include a separate line for the use of that lens WITH a filter as that would likely drive a different counter balancing weight. Simply put, a setup for a lens without filter would be different that a setup for that same lens with a filter.
As a photographer, the only filters that make sense to me these days are: UV filters to protect the lens, polarizers, and ND filters to increase exposure times in video.
One other wrinkle is the use or not of a lens hood. The use of a lens hood will also affect the balance and should be included in the listing.