Brainstorming is a process that should be done with a partner but here it's more like mapping the terrain.(Not testing my asssumption with a partner.)
is: I am under opponent on my fours and I have a grip on his leg.
2.Goal:my goal is to a) do a takedown b) pull guard c) take opponents back. My reactions debends on opponents moves. First, do I have a good grip on opponents leg (and his foot,too).
If I an deep under and have a good grip, is he trying to put pressure to my back (sprawling) or trying to pull a way. My options are a) pull his leg to my chest and sit back to tilt him on his back. b) to go forward and side and use shoulder of justice on his hip to break him on his belly c) to lift my butt up and do a wrestlers sit thru to take his back d) pull guard.
Even thou the situation is fairly specific, looks like goal is difficult to pinpoint. What you get depends so much on opponents reactions. At the moment my goal is to go with the flow so if he pushes, I should let him come forward, but redirect his mass or adjust my frames and grips.
Maybe the first question when on my fours and opponent is in front of me is:
1. Can I catch his leg ( go forward)? If not,
2. Can I catch his hand and go backwards? if not,
3. Can I lift my hip up, prevent opponent from getting to my side or back?
3. ProblemWhen under opponent in turtle one should cover his neck and collar. Also opponent might be looking for lock their arms under your armbit to turn you over and finish with darce/anagonda.
When opponent is attacking your neck, you also feel pressure and it's difficult to go forward.
(But opponents hands are at your reach and you can grib it, but you have to catch it first.)
Other problem is opponent taking your back. You can try to block him with your arm or back off and rotate to opposite side he is rotating to. If you have a grip from his leg, you can prevent him from taking your back - and it's good for you to go to 90 degree angle (Not directly under him.)
If you are flat on your belly, you have difficulties to move, but you can protect your neck easier.
One problem is not really seeing what is happening over or behind you?