I don't think holding FILMation rights would change Mattel's plans for the bio-storyline much. Nor do I think it would have changed figure release selections up until now, because I feel Mattel would have held back key 'A'-list FILMation characters as hostages to deliver 'buzz' and 'hype' for later in the line (much as they are holding back Sorceress and Ram Man).
However, if they had the FILMation rights, I do think there would be a greater effort to incorporate parts of that mythos into the storyline, such as a mention of the role of Enchantress in holding Miro prisoner and reference to time spent on Trolla and The Chimera in Marzo's bio.
Incorporating FILMation characters into MOTUC is essential in my view. There are so many great characters!
This MOTUC is our opportunity to have a full collection of MOTU figures spaning the whole mythos - and that has to include identities such as Shadow Weaver, Scorpia, Fang Man, Uncle Montork, Morgoth, Kothos, Shokoti, General Tataran, etc, etc, etc.
Mattel know we would buy FILMation characters. They need to pull their wallets out, buy the rights, and add these figures to the release schedule!!!