Yes, it is possible to edit the tech database in FS or FS2...
go to www.descent-network.com
and download the program under 'tools' called "VPVIEW32" or "VPVIEW*something*" i can't remember...
take that program, install it, open your Freespace directory and it's files, and find a file under folder 'tables' (in VP VIEW) that's called 'Ships.TBL'... extract that, then put it under (Freespace Directory)/Data/Tables/
(if the directory 'tables' doesn't exist under 'data' that's OK, just create one...if you don't know how to create a normal folder then please post again, and i can help you with that
) then open the file with notepad (click on it once to highlight it, then hold down left shift, then right click on the .tbl file, then click 'open with', and find 'notepad', click on it, and make sure 'always use this program to open this file' is NOT selected... ok, fine, you can select it if you WANT) then in the Ships.TBL file (opened now in notepad) you can edit ship speed, armor, weapon compatibility, etc. that's always good... and if you make a new ship, remember to make it 'player_ship'... also, at the bottom of each ship entry, is the 'tech database' thing or whatever, which has the picture and description, etc. for the tech database... at the beginning of the ship entries is the thing that says 'Player_ship' etc. make sure it says 'in_tech_database' too (i belive that's it) that will make the ship appear in the tech database... do the same thing for weapons.
Remember, a ship cannot hold a weapon unless it's given permission to in the ship.tbl file.