My conjectural possibilities right now:
1. Assault Ship
5000 DTon Military
Oriented around deployment of first wave planetary assault troops. Will have to include insertion support, self-defence, and basic fire support for groundside forces as well as casevac and resupply capability. The size of all of these components will determine if it is a battalion sized vessel, a company sized vessel, etc.
NOTE: If anyone can refer me to standard Marine assault TO&E for any Traveller Version, I'd appreciate it (I probably have the reference material...).
2. Hospital Ship
5000 DTon Military/5000 DTon Civilian
The Hospital Ship is the third line of medical care for a fleet on the move, after on-scene medics and ship's doctors/medstations. This is where more serious trauma victims and longer term care/regen cases are sent. The military/civilian distinction is whether the ship has self-defence armaments or is entirely unarmed. The ship will have to include transfer shuttles and such specifically geared to handling casualties.
3. Colony Ship
5000 DTon Civilian
When a colony is to be established on a new world, there is a need for a ship to take the colonists there in cold sleep along with enough gear to get them established, and the transport to get them and the gear down to the world's surface (or the ship itself has to land). If the ship is a landing configuration, the design needs to consider if the ship itself is then cannibalized for further colonial resources. In that event, a small jump shuttle or 100 or 200 ton starship may be a requirement to get the crew home or to maintain contact/resupply with the colony.
4. Mobile Base Vessel, Aquatic
5000+ DTon Military
The Imperium has a lot of water worlds. Sometimes, they even have to field forces to fight on these worlds. They also have sufficient resources to allow for some very specialized forces. In this case, the idea will be to have a ship crewed by races like Githiasko or Tursiops Galactis that can land in a water ocean and act as a mobile sea-floor (or continental shelf floor) base for underwater operations.
5. Virushi Free Trader/Envoy
x DTon Civilian/Diplomatic
Virushi are big. They take up a lot of space and conventional ships don't seem well suited to accomodating them. Yet they appear all over the 3I as far away as Capital/Core. One would think they must get around in various ways. This would be one such way, and would be a vessel usable by a variety of air breathing larger-than-normal beings (workstations and sleeping accomodations may need adjusted, but the basic design should work). The idea would be this would be a combination of Beowulf and Yacht (depending on fitting out) but made for 'larger than man-sized' critters.
6. Bwap Mobile Administrative Hub
X DTon Government
To the Bwap way of thinking, many regions of the Imperium are not yet sufficiently organized. Yet it can take quite a bit of time to build an effective civil service establishment in an area, both from the strictly physical side and the team-building aspect. Well, the Bwaps are nothing if not analytic and methodical. So thus was born the idea of a mobile administrative hub. The idea would be to pre-construct a vessel which, once landed and settled, could become a de-facto physical center for the bureacracy. It could have representatives of a single Imperial Ministry or many (depending on the need). The staff would be pre-constructed as well, and familiar with one another and evaluated for team dynamics in advance, so a smoothly functioning unit could be deployed all at once as needed.
This unit could be deployed to newly contacted planets, to areas recieving an upgrade in Imperial presence and services, or for catastrophe situations where Imperial oversight is required on short notice to deal with a disaster management situation or to replace a pre-existing Imperial bureacracy unit damaged or destroyed by war or terrorism or natural disaster.
Just land, open the main hatches, and the Imperial Civil Service is open for business. (Of course, I'm skipping over the mandatory pre-landing site survey, the various paperwork stages along the way, and sundry other protocols....)
Those are my current thought experiments. I want to see which ones I can get Ships for Windows III to spec out for me (so at least they'll be consistent in design).
the King Richard. I have been looking at that old ship again recently, but became frustrated with some problems in the official deckplans. I had started reworking it with an eye to sticking to the original as a for my own use project. That was proving difficult and the deck plans were diverging by neccessity. So now it's gonna be an entry here. Still very much like the KR in may respects it is a luxury liner for long slow tours of the Imperium by the ultra rich and powerful, full of potential for intrigue and adventure aboard 
