What is the SEO cost of splitting a large, slow loading page into several smaller pages?

Hopefully someone can help with an SEO / URL structure / Google spidering question.

I have a site that is well established, gets 100,000 visits a month and 95% of my traffic comes from Google searches.

I have a main 'funnel' page, lets call it Page A, that links to 50 other pages. These 50 pages then link out to the rest of my site (around 5,000 pages in total).

The problem is that Page A is taking a long time to load (up to 40 seconds), so I'm considering splitting it up into 10 seperate pages of 5 links each. Those pages will then link out to the 5,000 individual pages.

Page A doesn't get much traffic as most Google traffic comes directly to the 5,000 individual pages, but i'm a bit worried that Google will penalize me for messing with my site structure and the way its spiders go through my site.

Even though I will lose Page A's internal backlinks to the other pages, I will be re-creating them on the 10 new pages, so I'm hoping that won't affect my site overall.

Am I doing the right thing? Or should I keep Page A intact (but hide it / not link to it) and also create the 10 new pages? Or is there a better way to do this? Making the page load faster isn't an option.

Thanks!
Bryan