You are correct. It is your machine build it any way you want.
But don't ride it on public roads where others may be affected by a possible failure do to cost savings deem'd appropriate by the builder.... The public road thing makes it everybody's business.
I have seen more than a few stress failure's in my day. Most are caused by harmonic distortion. (vibration )
Alignment is very important as you state. But it doesn't solve the harmonic problem .
A builder recently posted pics of a Hawk frame that broke due to vibration. It was solid mounted.
I'm not here to beat you up but you stated that:
It has been proven time and again that you can't mount the engine in rubber and expect not to get excessive vibration. Get rid of your "dampeners" and mount the engine as solid to the bike frame as possible. I won't get any argument from any experienced builder here.
Wile I agree that soft rubber raped around the frame is a bad idea. I disagree and wouldn't advise any new builder to solid mount a motor in any machine for the reasons I have stated.
And yes I am an experienced builder.......