I think u've got your head in the sand, a decompression plate is a perfectly good method - granted it wont take the same abuse a set of low comp pistons will - but not everyone needs to run high boost. There are many many cars running decomp plates without problems.
It's like you're saying an rs turbo is a bodge unless its got aeroquip fittings throughout.
As for wellseal i have no idea how good it is or otherwise but...

"Good engine builders have been using it for years as it can withstand alot of pressure"

So u'd imagine it would do the trick, i think it puts an image of a "no more nails" type product in your head but obviously its not.

Erm DECOMP PLATE YEAAH!