Add command to fill the portal whit particles (like when you place water)
Command: /mvpm fill {water ; particle name}
Example: /mvpm fill enchantmenttable
Particles list: http://minecraft.gamepedia.com/Particles#section_1

Portal effects, please. :-)

I might be interested in sponsoring this effort financially if someone can give me a rough estimate :)

Hello,
Are there any plans regarding that feature? That would increase immersion/user experience of portals created with MV.
Thanks!

no, not at the moment. But it will be left open for anyone interested in opening a good PR to add this feature.