can hardly agree with any of that.
first if you want a total full replacement of gear, you only need 10 items (12 if barb). hardly space taking ever, no need for more tabs (we can buy additional ones too btw, iirc up to 4, but even if it were only 2, it’s going to be fine if you use it well). second you got it completely other way around.
your gear doesn’t depend on paragon, your paragon choices depend on the skills and gear you have (and the gear you have depends on the build you chose, since it has to boost your skills else it’s useless gear and you should salvage it and replace it asap, no stash space needed).
if you aren’t picking your gear in relation to your build, and aren’t picking paragon points in relation to your skills and gear to further boost what you decided your character must have, you are doing it terribly wrong so no reason to incentivate you in that nonsense giving you more space to hoard useless items.
if you build correctly and pick gear according to your skills and paragon points to boost skills and aspects, then you don’t need a single slot of stash more. your build is going to shine. and you don’t need to keep any other object but the ones you really need for your build, on any character, that is very few objects.
if you want to create another build, that is allocating entirely different skills, using totally different aspects and filling totally different paragon boards, you don’t need more space in stash.
you simply need a new character. you can leave all gear, aspects and paragon as they are on the one you completed, instead of trashing it.
just reroll an alt, levelling will be quick with secondary drops from your main and boosted stats from renown, you’ll have it full build asap, can profit of all new gear you wish (still just 10-12 items) and once you get past 50 start reallocating paragon points accordingly, to boost those new skills and those new aspects decently (of course if you dropped sacred or ancestral aspects with your main related to your second build, that will save you other time). again, no need for more space.
all that considered, not even counting characters inventory (which offers space for other 30 or so items in the backpack and 10 or 12 on the character itself), a stash tab has 50 slots. iirc you can get as many as 4. that is, 200 items. that is, 16 to 20 different full sets of gear (and as said even if we cut that in 2, you’d still have space for 8-10 full alts sets).
hardly any need for more space, thus. if you think you need more, it’s not a space problem on game’s side. it’s a hoarding problem, on your side. nothing the game can fix.