I think this might work if its framed like a feasibility study, rather than just a straight increase in costs that you can brute force.
A period of "pre-research", where tech progress is locked at 0% for X months, during which time, your scientists study
how you would develop a technology.
The period is longer, the further up the tech is from the "galactic tech level", whilst those at, or below it, have no feasibility study time.
On 3.2 I created a test mod adding breakthroughs and setbacks, using a similar process.
I summed up all "default" (not FE etc) empires, summed all empires with 1 tech in each tier, (repeated for P/S/E each) and took an average to get 3 values to establish the galactic standard in each discipline.
- Then if you researched a tech below the "galactic standard tier" you had a larger chance for a breakthrough every 6 months (10% per tier diff), which would randomly boost tech progress by 5-15%.
- Researching in the same tier as the galactic standard gave a small 5% chance for a breakthrough or setback.
- The same going the other way for setbacks, if you were in to T4 engineering techs when everyone else was on T3, you'd be getting frequent setbacks, randomly deleting 5-15% tech progress.
- If it helps, think of the above 3 lines describing an inverse normal dist for the breakthrough/setback odds.
- The amount added or removed by breakthrough/setback would be doubled if the tier-gap was 2+ (so researching a T5 tech when everyone is on T3 could give a 10-30% setback - or breakthrough [a vanishingly slim possibility])
- A custom notification at the top of the screen (not a popup) would also inform you of this.
It worked pretty well, though its the kind of thing that is easy to construct (and is not actually that intensive) but is not so easy to tune/balance.
It also helped - for me anyway - that it didnt make me feel like I was being penalised because others were behind, subjectively it felt like my scientists were just struggling with advanced technology.