Just a suggestion: why dont you make a Dom and write on both his and your scrappers Bio that they are nemesis. He doent need to be lvl 40. I usually do that with my own toons hehe
I have a dominator on Union, but he is a plant/thorns. Would normally do what you have suggested, however, would be good to actually fight my arch nemesis...
I also prefer playing melee characters, all my other alts...hardly get used, inc defs, doms, trollers + corr's.
Main 50 & Badger Nine Claws Claws/Regen/Body
Other 50's Ph10x Brute Unjust Law Tanker Samantha Urai Scrapper Codename 1250 Scrapper
Cepheus Defender Nilus Scrapper Electro Field Blaster S.PONGE Tanker
I recently tried fighting a spine/regen scrapper at lvl 40 with my plant / thorn dom in the arena...I choose to pass I'd rather have a nemesis I stand a chance of beating thanks.
Arena duels, 1 on 1, Dom's vs Scrappers are stupid. I've found my Plant/Thorns Dominator awesome in squishy fights tho', and I'm a n00b with it 
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If you want a mind/* dom to be your arch nemesis I would suggest you plan your build to specifically avoid any mez protection. As it stands you will two shot them without taking any significant damage in return. A more realistic nemesis would be a stalker with a similar build or a corrupter - especially a rad. If it must be a dom /psi at least has -regen so that would be a better option but still poor
Mind of Gaia lvl 50 Defiant's first Mind/Storm 'troller.
Deadly Doc 50 Dark/Dark Corr
and lots more on Pinnacle,Union and Defiant
meh regens are easy to fight when they cant heal 
Most regens are easy to fight for most pvp built doms.
Now SR... yikes I wouldn't touch that with a dom, unless Mind.
If you are a level 40+ Dominator, then I need your help.
My main character is a lvl 50 claws/regen scrapper....Because I like the build so much, I have rolled a new one. This new alt is a carbon copy of my main (same cossie and powers)...I am looking to write the description soon and this is where you come in!
I need a high level dominator (must have mind control), that can become my arch nemesis...
Those interested, can you please give a brief summary of your background....Many Thanks
Main 50 & Badger Nine Claws Claws/Regen/Body
Other 50's Ph10x Brute Unjust Law Tanker Samantha Urai Scrapper Codename 1250 Scrapper
Cepheus Defender Nilus Scrapper Electro Field Blaster S.PONGE Tanker