Couple of comments:
1. I dont like you having a whole risk section: the client hires MBB for a clear recommendation, which already takes the risks into account. Having a full blown risk section will sound like you are hedging your bets and dont really want to commit to a solution. If you really want to highlight a specific risk, id say something like "we understand the implementation is difficult, but we have experience doing this and would love to work with you on this"
2. Next steps and if we had more time are basically the same thing
Heres how id structure:
1. Ask for time to gather your thoughts. BCG will typically refuse btw, but still worth asking
2. Level set, remind us of the initial question
3. Answer first, "i have 3 recommendations, a, b and c"
4. Explain each recommendation: here's what i found, heres why it is relevant, here is what that will mean to you / upside + timeline
5. Next steps, either something we havent had time to analize, or selling the next project "let me help you implement"
All this can take 2 or 3 minutes - but done properly, every single sentence brings something new and is therefore needed. We only ever really complain of something taking long if you ramble and waste our time :)
Hope this helps ..