It might just be that this scenario doesn't work for you. If you aren't getting enough time and require more bonding then maybe you need another partner, or need to find someone that isn't as busy and keep him in your life as a really good friend or intimate friend (FWB). Here
is a link to a thread about how many is enough when it comes to partners. On average it seems that in order to even get a word in edge wise three to four is plenty... or less.
Most seem to do fine with two partners before coming apart at the seams due to lack of alone time to take care of oneself. This man would rarely have time for himself. I would hate to think if there were any major issues that come up. The whole balancing plate would tumble no? All those partners with needs and expressing them... ahhhh... overwhelming.
This is worrisome to me. I have three partners, four until recently, and I struggled with looking after my primary, myself. I still see that as my number one struggle. After several years of having many partners its easy to reach burn out. I would be very careful of that. Especially as he is asking you to share date time in order to kill two birds with one stone. hmmmm, not good... smells of burn out to me (having been there)
I would wonder why he needs so many partners and what "partner" means to him. Usually a persons needs are met with far less. Did he actually seek you out? Was he looking to date more? Is it a fetish of his to collect partners?