Yes, you can have new, stronger brackets fitted between the transom and the swim platform. Your local marine engineering shop can fabricate suitable brackets.
In Images 3 & 4 below, see the two new brackets Denis had fabricated and fitted to his Grand Banks 42.
The two original outboard brackets (made from bronze tubing) were left in place, one of which can be seen in Image 4.
The new brackets were designed to fit onto the original through-transom bolts. This minimized drilling new holes in the transom under the waterline and avoided any ‘retrofit’ appearance, (see Image 5 below).
For a ‘belt & braces’ approach triangular brackets may be fitted between the inside of the transom and an athwartship stringer; see Image 6 below.