To answer your question, NO.

You have to buy a retail copy of EFLC as you cannot mod the version bought from the marketplace.

Reasoning:
The files are different such as the script.img and script_network.img that you replaced the first time. These have all of the EFLC stuff in them like the new missions. If you want to use the same menus you use for Original then all you have to do is extract the .sco files using OpenIV and then put them in the new script.

Recommendation:
I would just download someone else's loader and use it as the base and use the mod slots to add the .sco's that you want to use. I used DSE's piece of crap base and just put my mods in the mod slots because I liked the way he set the mod slots up.

Any further questions? Feel free to PM me or post back on this thread and I will get back to you ASAP. Hope this helped. Good Luck!