I agree. It's sad to see your English longbows lose their extra range advantage and have to start over as infantry.
I've been thinking about the ranged hand-held weapon issue for a while now. How about this:
Archer (Antiquity) -> Crossbowman (Medieval) -> Mortar Team (Industrial) -> Rocket Team (Modern)
Both Ranged and Siege weapons cannot melee attack. Generally, a ranged unit, being man-portable weapons should be less in ranged combat value, yet we could also give them greater melee combat strength to hold a defensive line. While they would not be able to stand up to a huge pounding, they wouldn't necessarily immediately pop, and could hold off lower-tech attacks.
Ranged
Archer: 4 (6), R2, M2 (H40) - Archery
Crossbowman: 6 (12), R2, M2 (H120) - Machinery
Mortar Team: 20 (24), R2, M2 (H350) - Dynamite
Rocket Team: 40 (36), R2, M2 (H550) - Rocketry
Here are the common siege weapons, for comparison:
Siege Weapons (all have +10% vs. cities)
Catapult: 5 (11), R2, M2, set-up (H75, Iron)
Trebuchet: 6 (20), R2, M2, set-up (H170, Iron)
Cannon: 10 (26), R2, M2, set-up (H250)
Artillery: 16 (32), R3, M2,set-up, indirect fire (H420)
Rocket Artillery: 18 (46), R3, M3, indirect fire (H600, Aluminum)