Bracket & Enclosing Transom Value Destructive?

[Erasmus4]

I have a 1998 23 Silver King hull and am beginning the process of re-powering from the original pair of Merc 150 EFI Offshores. I'll hopefully end up with a set of Yamaha F150s and, given the added weight, put them on a bracket (Hermco?) and enclose the transom. My question here arises from a conversation with the local Yamaha dealer (he's also a Grady dealer), who was avidly of the opinion that in these boats, every time you make significant modifications to these hulls, you devalue them in the resale markets. Thus, he was strongly advising me not to take that route.

There are several good threads in this forum about bracket performance / structural characteristics, but I'd appreciate this group's view on his point. I have my own modest opinion, but has anyone dealt with this directly?