Yes you can run a fat sac in the back especially if you remove the rear seat or move it to the sunpad position (if the older boomerangs offered that option).
Yes, you can also put a tower on it but I don't think Moomba offers a Rad-A-Cage for the 'rang so you will have to get a generic one like the WakeDesigns unit.
If you are looking for a boarding boat the boomerang is not for you. Even with the tower and fat-sac you are not going to get a really big wake. If you are looking for a fun, little boat and primarily ski and occasionally board then it should fit your needs well.
That's my .02¢ good luck with your search.
Jonathan Hamilton
'99 Outback LS - with RAC and BB
Jonathan Hamilton
'99 Outback LS w/Ballast & Tower