Exactly. A chain with 0.01 BTC tail supply would need one million blocks (around 19 years) to produce 10k BTC. That should be slow enough to play it safe. The current block reward is 6.25 BTC plus fees. Let's assume that some block has 7 BTC reward. Then, you can grant miners 0.01 BTC for merged mining 700 times easier blocks on such sidechain. The difficulty of your altcoin can follow Bitcoin headers, it is that simple. And if 700 times easier difficulty is still too hard, then you can give miners less coins for mining easier blocks, and keep 10 minutes as a sidechain block time. Then, all miners will try to get tail supply of 0.01 BTC, and some of them will push your sidechain forward, if they hit a Bitcoin block at the same time.

Then look again at Paul Sztorc's triangle, and choose wisely: Merged Mining or big blocks? And if something else, then what it would be?