There seems to be a precident in BT that certain chassis that perfomr well sometimes form the bais of a new unit, in som cases being directly rebuilt into said new mech. There aren't any rules for this that I have seen, however.
The first such situation is where one mech's chassis is used as the basis for a new design. For example, the Wight chassis is fluffed as being refurbished panther chassis with new internals. Since you can easily change out the entire internals with a class E or F refit and basically make aa completely different machine, I am going to assume this can be covered under Herb's standard replies: you can replace all the stuff in a panther and tell everyone it is a Wight if it works for your game.
What isn't so clear is the next situation. Namely changing tech base and/or increasing chassis weight. Mechs such as the Marauder II and the Rifleman II are fluffed as being basically the same chassis and their progenitors with additional reinforcement to increase the mech's tonnage (ie structure mass increased). Others, such as Phaelans Wolfhound Grinner, or the original Warhammer IICs (presumably) take Inner Sphere chassis and replace them with Clantech. Can these sort of conversions be made under the rules, and if so, what refit level would this be?
