It would be useful if the 'techs' tab on the model dialog included a summary for each upgradeable model line with the current linear tech levels that could/would be applied to a new model. Maybe on the line below the top-tier of each model?
Also, an indicator for whether higher-tier weapons or armor have been researched since that model was developed?
Here's a bad mockup:

Could definitely be formatted better, maybe only display the tech differences that would be built into a new model designed now?
Also, the display of linear tech improvements should be modified -- keep the existing greyed out for not-yet-discovered but use yellow-highlighting for for discovered -- this would be a good reminder that I could plan for upgrading a model if I want to plan for it in a couple turns!
It would also be useful to have some kind of different color highlighting for tech bonuses that are currently being researched and where I would want to stop and think if I want to wait to upgrade that model. Something obvious-- instead of yellow text on gray, gray text against yellow background for that cell?