Size wizard

You have considered the spells enlarge and reduce interesting and decide to expand upon them and unlock their true potential.

Item shrinkage

You shrink an item to 3/4 of its original size taking up less space but not decreasing it's weight. level 2

Body part growth.

It lets you grow 2 bodyparts of your choice for 12 hours every rest
level 6

head+1int
eyes+increased vision range
feet+20feet movement
hands+2str
abs+1ac
level 10 the bodyparts become permanent still require a rest to change
level 15 you unlock the ability to give others a bodypart growth and it no longer requires a rest
level 18 you have +1 bodypart to grow for yourself and another

Weight change

It lets you change the weight of an item up to 1/8th or x8 of its original weight
lvl 10

Transmutation size expert

level 3 your training increases potency of  Enlarge/reduce 1.5x(or 1.25) size(of original limit) and to 2.5 minutes

level 14
Your time with using sizechanging spells in the transmutation class has increased the potency of reduce/enlarge to twice the size of the original and increase it's time to 5 minutes.
Increases damage of transmutation spells by 5%.

level 18
increases it's time to 30 minutes and Can use it on 2 targets at once and it is 25% more effective on yourself 2.5x size limit.

level 20
Increases reduce/enlarge to an hour and it is 40% more effective on yourself and 3 targets and the limit is 3x size of original .

Black hole

You can make a black hole(does 2d20 necrotic damage every turn for everyone within 20ft) by condensing 1kg of titanium it lasts 10 minutes(or shorter if you cancel it) and can only be done once per long rest.
level 18

Adjusted sizes

level 5
A weapon of a size to big for you can be weilded when shrunk 3/4


and when small you gain +2 dex -2str
and when big +2str -2dex
when level 10 you become more adjusted than this so -1dex when big and -1str when small unless it's using the upgraded version of reduce/enlarge in which case it is 
when bigger +4str -3dex
when smaller +4dex -3str

and can shrink a item to a quarter it's original size and it reduces weight making it a fifth of its original weight