(written from a Production point of view)
The Federation mission scoutship originated out of a 12 March 1998 script requirement of Star Trek: Insurrection, "On the viewscreen the attacking ship moves suddenly into view from a low density gas cloud like a destroyer emerging from a fog bank... it is a Federation Scout ship -- small but impressive, with windows at the forward cockpit...(Scene 33)."  Production Designer Herman Zimmerman has noted in this regard, "The script motivates everything. We create what is needed to tell the story. In this scene, we have two craft that must appear very different from one another in order for us to understand this part of the story. Visually, we have to know that Data is in a Starfleet scoutship, but not a scoutship that came from the Enterprise. That presents a problem. We have to design the scoutship in a way that identifies that ship and separates it visually from the second ship, which is the Enterprise shuttle. The audience must be able to know immediately whether they are looking at one ship or the other, both inside and out. The exchanges that are taking place between the ships are very short and abrupt, but there must be no mistake that you're either in the scoutship with Data or in the shuttle with Captain Picard and Worf." (Star Trek: Action!, p. 188)
Giving form and substance to the scoutship was a task that befell to Illustrator John Eaves. Eaves, as designer, stated, "What they asked for was kind of a combination of a runabout and the Defiant. So I kind of used the overall Defiant shape, where the nacelles are encased as opposed to being external, as they are on the Enterprise and other Star Trek ships. That gives it an aerodynamic kind of shape. I gave it a wraparound canopy. It's pretty mich a mini-defense ship, and Data makes use of those qualities." (Star Trek: Action!, p. 190) Further elaborating, Eaves has stated, "I repeated certain shapes throughout the federation designs, so the ships all seemed to extend from a single technological base. The scout ship flown by Data is a good example, as it used the cowled enclosed engine nacelles seen on Star Trek: Deep Space Nine's starship, the Defiant. That look suggested heavy shielding, which went well with streamlined, high-performance fighter appearance." (Cinefex, issue 77, p. 72) Eaves is also on record stating, "We also had a scout ship for Data, which was kind of based on the Defiant lightly. The producers wanted to see something that followed something from the Federation and Starfleet. And so we kind of based it roughly on the Defiant. It is more of a single, two-man ship, as opposed to a big fighter like the Defiant is. We used the same kind of color schemes, the bare metal look, and it was actually designed in a way, so both ships [remark: with the Type 11 shuttlecraft model] could interact together." (Star Trek: Insurrection (Special Edition) DVD-Special feature "Production:The Art of Insurrection") On another occasion Eaves noted, "The scout was very fun. They just said a type of Defiant-class ship, so I designed it around the same elements. The nacelles were built inside the ship - they are encased as opposed to to being exterior - and everything has heavy armament around it. I kind of went with more of a streamlined look. The side really has a bulky feel to it; it's meant to be an attack vessel so it has a heavy profile, but from the top it is very streamlined. For the outline I wanted to go with something that was very distinct from tradition on the top and more aesthetically pleasing shape from the side." (Star Trek: The Magazine Volume 1, Issue 4, p. 30) Eaves finished up upon the design work in January/February 1998. However, a very small adjustment was made to his design, "The windshields are very significant, because Picard sees Data in the window of the scout and vice-versa; Data sees Picard in the shuttle. At superspace speeds that's probably stretching things a bit–but we're going to do it.", Zimmerman added. As a result Set Designer Nancy Mickelberry added mullions to the cockpit of Eaves' design, which were carried over to the final CGI-model, shown in an early 1998 top view orthographic design view. (Star Trek: Action!, pp. 189-190) It, years later, solicited this response from Eaves, "Yes the defiant was the lineage for the architecture!!! The smaller cockpit area was script driven although it is kinda nice to have a smaller piloting area unlike so many of the other ships that have huge amounts of room with very little glass to see outside!" 
CGI model Edit
For Insurrection, the producers decided to complete the transition into the digital realm and that this feature would be the first movie completely without the time honored motion control model photography. However, in this stage of the technique, that meant that the CGI-workload had to be divided between two VFX-houses, Santa Barbara Studios (SBS) for the outer space shots, and Blue Sky/VIFX for the planet bound effects. Though the scoutship was prominently featured in the in-atmospheric locked together scene with the Type 11 shuttlecraft model, its first appearance was in outer space, so the task of building the CGI-model fell to Santa Barbara Studios. Being a relatively early outing at the time into the realm of CGI, solicited the following remark of Eaves, "The CGI guys needed every possible line drawing. They wanted all the details in advance–which differed from the way I usually work with traditional modelmakers, leaving areas open for them to contribute. But Santa Barbara did not want to have to go through an approval process on every aspect of these ships–which made sense, because there wasn't time to make that happen while still getting the ships modeled and animated and rendered out. It was a learning experience for me to provide these detailed technical drawings." (Cinefex, issue 77, p. 72) Detailed scale comparison charts, originating from this desire has made Eves set the in-universe dimensions of the scout at 80×50 feet. The model was executed in the Maya CGI software.(Sci-Fi & Fantasy Models, issue 34, p. 29)
The scoutship was never again featured in later later representation, beit on-screen or in print. There actually was a reason for this, as Star Trek: The Official Starships Collection project manager Ben Robinson has indicated in 2015 that the original model computer files were no longer in existence, due to Paramount Pictures's failure to maintain ownership over these, as well as due to Blue Sky/VIFX' own demise, "Never found the CG models from Insurrection...so we're rebuilding them! Makes me feel like Dan Curry." , he explained, "I'm working on this [remark: Son'a ships for the Collection] at the moment. It's tricky because the company that made the CG - Santa Barbara Studios didn't archive them and used their own software. Nothing is impossible though and I do have perfect reference [remark: referring to renders he had received for the Fact Files years earlier]."  Still, Robinson had slated the scoutship to become one the first two Insurrection outings in his collection, based on newly reconstructed CGI models.