My new 1/72 figure converted for Halo-ish Diorama

Here are some progress pics of my figure conversion. I think I've spent about 1.5 hours on this little dude so far and he hasn't even been painted yet. I'm mostly done the modeling though I think. I used Revell of Germany's Modern Germany infantry figures as the base and I'm trying to convert them into the marines from Halo, the game series. I'm a big fan of the games and wanted to model some of the things, but since there are no kits I had to do it myself. I haven't gotten the guts to do a vehicle yet and haven't found any good kits as a base for a warthog. I would also like to find some good figures to base for some ODSTs. I used Squadron Green putty, superglue and a dull knife to convert it. It isn't exactly true to the games but it is good enough for me. Also I've just been making up little scenarios and backstories for fun. Things like the reserves are running low and old outdated equipment is being made do with. Most of them are gonna be set in a desert wasteland-ish type setting or urban metropolises (link in my "www" on the bottom to my "big" dio).

Let me know what you think and what I could improve on. Also if anyone knows of any good 1/72 (or close) figures that would work for converting into ODSTs or even a Master Chief figure would help. Maybe even if you see some good 1/35 figs to convert. Anyways heres some progress pics, can't wait to paint him.