you could argue that is what the current model is... the 4 most recent seasons are 90 something % of the weight, and the more recent is heavier. i would be fine with the d1 model too but i'm assuming that is more work.
30%, 21%, 15%, 10%, 7%, ... is the progression at 30%. then the last 4 are only 76% and the prior handful of seasons are going to make up most of the rest, functioning almost as a baseline prestige of sorts. that may be a little low though. i just picked 30% randomly. maybe 40% is better
40%, 24%, 14%, 9%, 5%... that is the 40% progression. so the last 4 would be 87% of the total, which sounds a little better.
anyway i'm all for either i just am throwing out what i think is easy and therefore more likely. 'can you drop the most recent season's weighting from 50% to 40%' might come across as far more doable to a developer new to a codebase than 'can you convert d2/d3 to the d1 prestige model but without baseline'