Simple Madass : Rear Brake Caliper Replacement

As I found that the rear brake of my madass is not really grippy compare to the front one, i thing this rear brake need an upgrade. But what kind of upgrade is needed? Some options I can thinking of :
1. Change rear master brake with bigger volume. I have been thinking of nissin 14mm master brake, but for sure it will need a lot mod to mount it (different shape). Another option is to replace the master brake with kitaco or ninja250 rr or Honda rear master brake, but eventhough the shape is similar, the screw spacing hole to hole may be different (i have bought kitaco and the screw spacing hole is farther).

2. Replace the brake shoe pad with grippier one. For this reason, i found that this caliper Match with the front caliper of Honda GL Pro, so an OEM Honda brake shoe will be better compare with the stock one. I don't know why in my case the stock caliper won't slide with the new brake pad installed, but 2 spacer solve the issue by moving the stock caliper away so the brake pad is not pushing the disk all the time.

3. Change the rear disk brake with gripping one, but it's so hard to find the correct size with the same mounting hole, and as well i don't know what material give better grip.

4. Change the rear caliper with better design. I was thinking of replacing this with rear caliper set of Suzuki FU150 (nissin one piston) but it may need a change in the rear bracket. I don't know if this set will be a drop in replacement, but i have a doubt which one better, one piston vs two piston caliper? Then, if two piston is better, which one is better between two piston in one side or one piston in each side? I think i will go with hardest route by choosing 2 piston design (one piston in each side). Why? Because i can have brembo in my rear brake. The rest is just to make the new bracket to fit brembo rear caliper into madass stock bracket.. If this work, i may sell the bracket to my other friends in local madass community, why not.. It's brembo in madass..

So, until the bracket for my new brembo caliper done, i need to rely on the stock caliper with honda brake shoe. Not bad, but i want more.. A brembo in madass..we will see how better in can be..