No I don't really know how to do it but if there is a way I know how it would be done. TWL is one of the first partitions on NAND. So you won't have room to expand it without conflicting into other NAND regions like AGB_SAVE, FIRM0 and FIRM1 and CTR_NAND partitions. You'd have to move TWLN to the end as the last partition and patch TWL_FIRM to read from that instead. That also means patching NATIVE_FIRM so that it installs new DSiWare to the correct partition location. So two things have to be patched before it would work.