I think a blanket "seconds of control" rule isn't necessarily the way to go.
BJJ competitive rules have traditionally typically awarded points for transitions into control positions, not for the control position itself. That's one thing that differentiates BJJ competitions from other gi-grappling styles.
Guard passing is the most obvious example: the points are awarded for escaping the guard and ending up in an advantageous position - which incidently generally implies achieve some control post-pass.
Rather than implementing x-seconds rules, I'd like to see something like the following (I'll keep it simple):
Guard Pass awarded when the passing player has evaded entaglement of their opponents legs and is in a superior position.
Mount is awarded once contact has been established with the ground with both legs (be it knees or whatever) whilst transversing the opponents torso.
Knee-ride is awarded once then classic knee-torso-foot position has been adopted.
The one thing that might make a difference is the introduction of a "Point Esculation" rule = points can oonly be earned if:
1/ you're increasing the amount of points you previously earned (e.g., going from Knee-Ride to Mount = 6 pts (2+4) but Mount to Knee-Ride doesn't earn 2 points because you're not esculating the attack);
2/ if your opponent scores on you between your point scores; or
3/ if a neutral position is adopted between point scores (Neutral = implies a loss of control (non-superior position), any form of Guard or substaintial break of contact between the combatants).