RPing things that exist outside of the bounds of the game mechanics but are also quite reasonably possible within the limits of the fictional setting requires that all parties involved abide by a "gentlemen's agreement" (pardon the gender-specific term) as to what resources and abilities can be used and how things are resolved. This veers into the collaborative storytelling side of roleplay where, if we were sitting around a table, very few if any dice would be rolled and sourcebooks rarely referenced in favor of fashioning a more interesting and fast-moving narrative.
The problem is that EVE exists not around a table with a GM to oversee and supervise, but on a vast stage with no one really in charge. People will get offended if, via the client, you start playing around in EVE-the-fictional-universe in ways that stray outside the rules and limitations of EVE-the-computer-game. Personally, I try to be very tolerant of the sort of improv you're talking about Nikita. After all, it's something that I've done to a considerable degree with various levels of success. I have found, however, that when other players have been willing to meet me around that metaphorical table, we have created some of the most enjoyable RP interactions I've had in EVE.
Edit: A follow up specifically addressing "marines" and other such face-to-face combat things. I've always been wary of this primarily because of how little small unit combat figures into my appreciation of the setting. Infiltration, espionage, sabotage (hacking, sure, of course), and propaganda seem to fit New Eden better than battalions of soldiers and heavy artillery. Naturally, that will change soon with Dust and has been less and less the case since TEA anyway. Like everything else, however, this can be done well and it can be done poorly. As an example of the former I think of Saxon Hawke's abduction or even the kidnapping tit-for-tat storylines RIA ran with Seri (let's discount the less than cordial afterglow from that). Hell, even Seri staging a trial and hanging traitors to the Fed was an interesting, if dark, angle to take. Done poorly, I think of Ber Kan and all the mucking about on IGS about this-and-that regiment of Caldari light infantry.